U» S. DEPARTMENT OF AGRICULTURE. 

BUKBAU OF ANIMAL INDUSTKY. 



SPECIAL REPORT 



ON THE 



EMD 



RESULTS OF EXPERIMENTS 



CONDUCTED UNDER THE DIRECTION OF DR. D. E. SALMON, 
CHIEF OF THE BUREAU OF ANIMAL INDUSTRY. 



BY 



THEOBALD SMITH, Ph. B., M. D. 



PUBLISHED BY AUTHORITY OF THE SEOKETARY OF AGRICULTURE. 



WASHINGTON: 

GOVERNMENT PRINTING CFFi'JE. 
1891. 






NOV 141906 

i).ofa 



TABLE OF CONTENTS. 



Page. 

Letter of transmittal 7 

Investigations concerning the nature and etiology of swine plague 9 

Introductory <j 

Brief description of the methods employed in the investigations 11 

Brief summary of the earlier investigations of swine plague (1886-1888) lU 

In Illinois 19 

In Iowa (1886) 2:{ 

In the District of Columbia 2:5 

In Maryland 27 

In Iowa (1883) 28 

Investigations of 1889-1890 31 

In the District of Columbia ;',1 

In New Jersey 57 

Swine-plague bacteria, general characters 85 

Resistance to destructive agents 90 

Pathogenic action of swine-plague bacteria 93 

Effect on small animals .-. ..^.i-.....-. 93 

The disease in awine as produced by the inocnlation of cultures 97 

Swine plague as observed in epizootics 98 

Disease of the digestive tract in swine plague 102 

Attenuated swine-plague bacteria in sporadic cases of pneumonia, in septic 
diseases of swine, and in the upper air passages of healthy swine and other 

domesticated animals 109 

Other investigations of swine plague 118 

American 118 

European 125 

Practical observations 133 

1. Conditions which may favor and oppose outbreaks 133 

2. Distribution and transmission of swine-plague bacteria 135 

3. Relation of hog cholera to swine plague 138 

4. Relation of swine plague to diseases of other domesticated animals 141 

5. Measures to be taken in the prevention of swine plague 145 

Conclusions 149 

Appendix. — The presence of septic bacteria probably identical with those of 

swine plague in the upper air passages of domestic animals other than 

swine, by Dr. V. A. Moore. 151 

Description of plates 101 

3 



LIST OF ILLUSTRATIONS. 



Page. 

Plate I. Normal lungs of pig, inflated, lateral surface 163 

II. Same lungs, diaphragmatic surface 163 

III. Hepatization of lung with pleuritic exudate 163 

IV. Same luug with adherent portion of diaphragm 163 

V. Hepatization of luug with necrotic foci 163 

VI. Pneumouia, pleuritis, and pericarditis produced hy inoculation of 

swine-plague bacteria 163 

VII. Caseous degeneration of lungs in swine i^lague 163 

VIII. Caseous masses in lung tissue. Masses of exudate in large intestine. 163 

IX. Collapse and broncho-pneumonia 163 

X. Pericarditis in swiue plague 163 

XI. Swine-plague bacteria (highly magnified) 163 

XII. Swine-plague bacteria in cultures w 163 

5 



LETTER OF TRANSMITTAL. 



Washington, D. C, July 20, 1891. 

Sir : I have the honor to submit herewith the second special report 
upon the investigations of infectious swine diseases. Tlie lirst report 
dealt mainly with hog cholera, while the accompanying report is de- 
voted to swine plague. 

In this volume the investigations are reported in detail which have 
led up to a separation of swine plague as an independent disease from 
hog cholera. The difficulties surrounding investigations of infectious 
swine diseases have been very much increased by the frequent associa- 
tion of both hog cholera and swine plague in the same herd. This 
has necessitated frequent repetitions of investigations before positive 
results could be obtained. 

The importance of thoroughly scientific investigations of infectious 
animal diseases is becoming more and more apparent, and, owing 
to the commercial interests at stake, the subject is now assuming an 
international character. Even though investigations of this nature 
do not at once suggest the means of dealing satisfactorily with such 
diseases, it is, nevertheless, essential that we should know as much as 
possible of the nature of every one of them within our boundaries if 
we expect to bring to bear upon them all the knowledge which is 
accumulating so rapidly in various parts of the civilized world. The 
investigations in this report prove the existence of a virulent swine 
disease due to specific bacteria and its identity with the disease of 
Schtveineseuche, prevalent in Germany. It also demonstrates the wide 
distribution of this class of bacteria, chiefiy as varieties of feeble 
disease-producing power in the upper air passages of various domesti- 
cated animals. It is not improbable that this group of bacteria may, 
when exceptionally virulent, attack other domesticated animals, and 
indeed we know that tlie bacteria of at least one form of fowl cholera 
can not be distinguished from those of swine plague by the bacterio- 
logical methods now in use. In short, this group of bacteria which 
appears to have a world-wide distribution, may be considered as very 
dangerous to our domesticated animals, and, consequently, the care 
with which they have been studied, more particularly with reference 
to their disease-producing properties, is fully justified. 

With the publication of this and the preceding volume the informa- 
tion is given by which a diagnosis can be made of the two principal 

7 



8 

infectious diseases to which our swiiie are subject. The nature and 
cause of these diseases are made clear, and knowing these, we can 
apply the curative and preventive measures which the progress of 
medical science has made possible, or which future researches may 
show to be available. 

D. E. SALMON, 
Chief of the Bureau of Animal Industry. 
Hon. J. M. ElJSK, 

Secretary of Agriculture. 



INVESTIGATIONS CONCERNING THE NATURE AND ETIOLOGY 
OF SWINE PLAGUE. 



INTRODUCTORY. 

Since 1886 the bacteriological investigations carried on in the labora- 
tory of the Bureau of Animal Industry on infectious swine diseases 
have revealed the existence of pathogenic bacteria differing markedly 
from those causing hog cholera. They preferably attack the chest 
organs of swine, the lungs, and serous membranes covering these vital 
organs. The difLiculty encountered from the beginning in obtaining a 
clear understanding of the action of these disease germs is the frequent 
mingling of hog cholera with this disease, which has been called swine 
plague. In some outbreaks only hog-cholera bacilli are detected, in 
others only swine-plague bacteria, while in the majority of outbreaks 
thus far studied both bacteria are associated together. This condition 
is very likely due to their wide distribution over the country. 

The importance of swine plague bacteria is not limited to swine dis- 
eases alone, for they belong to a group of bacteria which in various 
parts of the world have attacked other species, such as cattle, horses, 
game, and fowls, and the question whether there may not be a trans- 
mission of such diseases from one species of farm animals to another 
must not be lost sight of. 

The swine-plague bacteria have been very carefully studied in view 
of their importance, and attention has been given more directly to their 
pathogenic effect on the smaller experimental animals, such as mice, 
rabbits, guinea-pigs, pigeons, and fowls, in order that a proper under- 
standing of their relative virulence could be obtained. Investigations 
in various diseases have brought to light bacteria which, although iden- 
tical so far as we are able to determine, vary greatly in their virulence, 
and it seems now that the relative virulence or disease-producing power 
must be looked upon as the chief criterion of danger. Feeble virulence 
signifies a feebly infectious localized disease. A high degree of viru- 
lence signifies the power to spread and perhaps to attack other species. 
This imiwrtaut factor of virulence can only be measured by the inocula- 
tion of animals of various degrees of susceptibility. The great variation 
in the virulence of both swine-plague and hog-cholera bacilli has been 
demonstrated in this way, and when we come down to the lowest grades 

9 



10 

the problem arises, can such varieties produce disease at all, aud are 
they not merely accidentally present ? An answer to this question can 
not be given categorically at present, and its solution will demand con- 
tinued, undivided attention to this subject of disease germs for some 
time to come. 

Another fact, the significance of which has been discussed in the 
text, is tlie existence of bacteria in the air passages of various domesti- 
cated animals during health, which are not distinguishable from swine- 
plague bacteria excepting by feebler pathogenic effect. 

The question whether swine plague is an infectious disease by itself, 
demanding the attention of the veterinarian, the agriculturist, and the 
Government, was practically solved, though not absolutely demon- 
strated, by the investigations of 1887. The repeated attacks upon this 
work made it desirable to spend much more time than was actually 
necessary in the investigation of outbreaks as they came within reach 
of facilities from time to time, and now a large amount of material has 
been collected which fully confirms the position taken in 1887, that 
there are at least two swine diseases of an infectious character. These 
have very likely existed together for a long time, but a differentiation 
could only be effected by the advanced position of bacteriology and the 
ample means provided by the Government. 

The frequent association of hog-cholera bacilli with swine-plague 
bacteria has made it necessary to pay some attention to hog cholera as 
well. Thei^e investigations are based on the facts already published 
on hog cholera and the bacillus of that disease in the special report on 
hog cholera (1889). This report is therefore necessary to an under- 
standing of the contents of the present volume so far as the strictly 
experimental portion is concerned. 

It is to be hoped that these investigations will prove not only of ad- 
vantage in the protection of swine from disease, but will be a basis for 
the investigation of diseases of other domesticated animals due to this 
group of bacteria, which may appear at any time owing to the growing 
complexity of intercourse between different sections of the country, 
modifications in the methods of stock-raising, etc. 

It must not be assumed that our knowledge of the etiology of swine 
diseases is complete even with the advances made thus far in swine 
plague and hog cholera. There are important questions with reference 
to both diseases which demand elucidation. Especially is it desirable 
to investigate those outbreaks more carefully in which we find the ap- 
pearances of hog cholera without the bacilli in the internal organs. 
The complete mastery over a disease is only to be obtained by complete 
insight into its causes. If all the suggestions derived from scientific in- 
vestigations, conscientiously applied, fail to prevent the appearance of 
a given disease it signifies that our information is as yet incomplete, 
and that there are some still unknown channels through which the 
bacteria of such disease are distributed. 



11 

To devise ;i proper plan for an intelligible presentation of the inves- 
tigations and results which will be satisfactory to those who are not 
immediately interested in the investigations, and simply desire to know 
the deductions so as to be guided by them, has been a diflicult one, and 
has demanded the occasional repetition of statements. In general all 
those facts not necessary to an understanding of the text have been put 
into smaller type. All the investigations proper, including a detailed 
description of the various outbreaks, autopsy and bacteriological notes, 
test inoculations of swine and smaller animals, have been kept together 
under the respective outbreaks, while all essential information derived 
from these investigations and experiments is to be found in the subse- 
quent sections of the report. 

The contents, therefore, have been arranged in the following order : 

The methods of work are first described, followed by a brief review of 
earlier and a more detailed account of later investigations. Then come 
a general description of the swine-plague bacteria, of their disease-pro- 
ducing power, and some facts showing the wide distribution of this 
group of bacteria among domesticated animals in a healthy condition. 
A chapter is also added, giving a brief account of the investigation of 
others in this field. Lastly, all the results and practical observations 
which may be of value to the farmer are brought together. 

The writer acknowledges the continued assistance since 1886 of Dr. 
F. L. Kilborne, veterinarian of the Experiment Station, who has had 
charge of the experimental animals, has assisted in mauj' of the post 
mortem examinations, and has performed the inoculations upon swine. 
In the laboratory, Dr. V. A. Moore has assisted, since 1888, in general 
pathological and bacteriological work. The special services of these 
gentlemen are also referred to in the text. 

BRIEF DESCRIPTION OF THE METHODS EMPLOYED IN THE INVESTI- 
GATIONS. 

The difficulties that are met with in the investigation of infectious 
swine diseases are not those usually encountered in bacteriological in- 
vestigations. In the first place outbreaks occur as a rule some distance 
from a laboratory. Yet the amount of bacteriological work demanded 
by each case, in order that any conclusion may be reached, can not be 
done excepting in a well equipped laborator3\ Hence it has been our 
effort to transfer, if possible, cases of the disease to the Experiment 
Station, and also to keep up the disease there by exposing fresh cases. 
In fact, only those investigations carried on in this way can be regarded 
as complete, while cultivations made in the field are at best restricted 
to a few or only one organ, and plate cultures are out of the question. 

Another difdculty is due to the belated information which we obtain 
of any given outbreak. Usually from one-third to two-thirds of the 
herd have perished before the investigations are begun. This is unfor- 
tunate in swine plague, because the earliest cases are the most satis- 



12 

factory from a bacteriological standpoint, since the swine-plague bacteria 
are most easily demonstrated in such cases. It seems that the infection 
passes through a herd quite rapidly, and those animals which live long- 
est have reached a stage of the disease in which the swine-plague 
bacteria may have entirely disappeared. 

A third difficulty to be contended with is the rapid death of the ani- 
mals, which makes a thorough examination of each animal impossible. 
The alternative before us is either to limit our examination to a certain 
number of organs in every animal, or else to examine a few very 
thoroughly. While we have endeavored to meet both demands, of ex- 
amining every animal, and also doing it as thoroughly as possible, we 
have but partially succeeded in this, owing to lack of facilities and 
assistance. The pathological changes differ so much from animal to 
animal, the extent of the organs involved varies to such a degree, that 
there is a great temptation to examine every animal in the hope that 
most information can be obtained in this way. 

The investigations consisted in watching the course of the disease in 
the infected animals, in post-mortem examinations of those that died, 
in microscopic examination of the diseased tissues, fresh and hardened, 
and in bacteriological examination of a certain number of organs. The 
post-mortem examination included the various organs and tissues, with 
the exception of the brain and spinal cord, which were exposed in a 
very few cases only. The skin was first reflected from the thorax and 
abdomen, the abdomen carefully opened, and the spleen or a portion of 
it first removed with sterile instruments and reserved for further ex- 
amination. From any fluid or exudate present a minute quantity was 
transferred to culture media by means of a platinum wire bent into 
a loop about three to four millimetres in diameter and soldered into a 
glass rod. The thorax was next opened by removing the sternum, and 
from any effusion or exudate cultures were made at once. The vari- 
ous organs destined to be used for bacteriological examination were 
removed in whole or in part before being soiled. 

Portions of organs designed for microscopical examination were in 
part examined fresh by making sections with the razor, teasing, etc., 
in part hardened in 95 i)er cent, alcohol and infiltrated with paraffin 
before the sections were made. These were stained in different ways, 
chiefly in alum carmine and in alkaline methylene blue (Loffler), which 
was found most satisfactory in bringing out the swine- plague bacteria. 

The various cultures were made in the following manner: With a 
platinum spatula a small area of the surface of an organ was thoroughly 
scorched, and from the scorched area minute particles of tissue were 
cut out with flamed scissors and forceps, the scorched layer being 
rejected. These particles were then transferred to various media for 
tube and plate cultures and also used for the inoculation of animals. 
Another mode of inoculating cultures used was to pierce the scorched 
area with a straight stiff platinum wire, which was then stirred about 



13 

in liquefied media or rubbed over the surface of agar. In this way- 
only a minute trace of the parenchyma could be transferred, and it 
was only used when bacteria were numerous enough to be detected 
under the microscope. In the notes given with the various outbreaks 
the platinum loop and wire mean respectively the looped wire and the 
straight wire. Note is merely made of this to indicate the difference in 
the quantity of material used to inoculate the culture media. 

The more usual method in vogue of disinfecting the external surface 
of organs by placing them in a 5 per cent, solution of carbolic acid or 
a one-tenth per cent, solution of mercuric chloride for a short time, 
then making several incisions in planes at right angles to one another 
into the depth of the organ, was not employed, because the method 
already mentioned of scorching a small portion of the surface seemed 
safer and more satisfactory. When cultures were inoculated with 
blood this was done from the right ventricle while the heart was still 
in situ. The thin ventricular wall was scorched over a small area, 
then the edge of the spatula was used to burn through. The platinum 
wire or loop, or the glass pipette, if blood was to be collected, was 
inserted through the hole thus made. The same methods were employed 
in the examination of the small exi^erimental animals. 

For the cultivation of swine-plague bacteria agar-agar as usually 
prepared with bouillon, peptone, and common salt, and the ordinary 
peptone bouillon, are the best media. In the earlier investigations 
nutrient gelatine was chiefly employed, but it was found that some 
varieties of swine-plague bacteria may refuse to multiply in it, hence 
it was discarded. In addition to plate cultures for the isolation of these 
bacteria the inclined surface of agar in tubes is of great service. In 
many cultures the colonies appeared completely isolated on the agar 
surface, thus enabling us to start from single colonies when plate cul- 
tures had not been prepared at the same time. 

For the inoculation of smaller animals with bacteria from cultures 
two methods were employed : (1) A small pocket was made in the sub- 
cutis by an incision through the skin with sterilized scissors and a loop 
of the growth rubbed into this jjocket ; (2) liquid cultures were pre- 
pared by inoculating peptone bouillon and allowing theliquid to become 
clouded in the thermostat or by transferring the growth from agar 
tubes into sterile bouillon or water and making a suspension. The 
liquid was then injected with a hypodermic syringe into tbe sub- 
cutaneous tissue or into a vein. The hypodermic syringes used were of 
the ordinary pattern, since the various others devised, such as the Koch 
syringe and the asbestos-packed syringe, were found leaky and ineffi- 
cient and did not enable us to inject a definite quantity with accuracy. 
In this investigation these syringes could the more easily be dispensed 
with, since both swine-plague and hog-cholera bacteria are sporeless and 
killed by disinfectants in very dilute solutions. The syringes and 
needles were disinfected both before and after use by filling them with 



14 

5 per cent, carbolic acid and allowing this to remain for 15 or 20 minutes. 
The acid was then removed with boiling water. Great care was taken 
that no fluid passed beyond the piston. If it did the syringe was taken 
apart and the parts immersed in 5 per cent, carbolic acid. While this 
method of making injections may seem theoretically objectionable, it 
has nevertheless at no time proved the source of any accidental infec- 
tion. This method is not applicable, however, to bacteria which pro- 
duce spores, or which prove very resistant to disinfectants, such as 
anthrax and tuberculosis. In general syringes were dispensed with 
and the first method employed when the accurate measurement of the 
quantity of virus to be injected was not essential. 

The technical difficulties surrounding the problem of the causation 
of swine diseases are mainly due to the intermingling of two diseases, 
hog cholera and swine plague. As this problem will be discussed fur- 
ther on, only those points need be considered Ijere which involve the 
methods employed. The important question to be decided in every 
outbreak is whether one or both kinds of bacteria are present. This 
can only be determined by bacteriological investigation. It is evident 
that to examine every organ of every pig bacteriologically is a task of 
enormous dimensions, hence the simplest reliable method must be em- 
ployed. At first thought it would seem sufficient to make plate cultures 
from the various organs and examine the colonies as they develop. 
There are, however, objections to this method taken alone. Certain 
varieties of swine plague bacteria, especially the most virulent, do not 
as a rule grow in gelatine, while on agar the colonies of hog cholera can 
not be distinguished positively from those of swine plague, unless the 
bacteria composing these colonies are examined. For a rapid and reli- 
able determination of the presence or absence of these two kiuds of 
bacteria, I have found in addition agar and bouillon tube cultures nec- 
essary. The motile hog cholera bacilli are detected at once in the 
bouillon and in the condensation water of the inclined agar cultures. 
Such cultures may then be plated, and fresh cultures of the hog-cholera 
bacilli and the swine-plague bacteria obtained by inoculating from 
isolated colonies. These cultures are then in condition to be tested on 
smaller animals to make the diagnosis complete. While it is desirable 
that when both kinds of bacteria are present they should be isolated 
from as many animals as possible, it is obvious that the presence of 
virulent hog-cholera bacilli in a single animal of a herd leads to the 
inference that they are most likely present in all the remaining diseased 
animals. 

The detection of swine-plague bacteria in liquid cultures containing 
hog-cholera bacilli is, as a rule, not difficult. The best method consists 
in the examination of the liquid unstained in a drop suspended from 
the under surface of a cover- glass resting on the margins of a cell on 
or in the slide. The most convenient cell I have found to be a thin 
glass ring fastened to the slide with Canada balsam. A little glycerin 



15 

is placed ou the ring so tliat when the cover glass with the drop on it 
is inverted and laid on the ring the immersion lens will not draw it up. 

The hog-cholera bacilli are readily detected in this drop by their 
motion.* If the border of the drop be examined, the two kinds of bac- 
teria may then be distinguished by a slight difference in size in favor 
of the hog-cholera bacilli. \Vheu the growth from the condensation 
water of agar cultures is to be examined, it must be diluted with bouil- 
lon or sterile water kept preferably in tubes, just as the bouillon is, in 
small quantities. The examination of cultures in this manner can not 
be dispensed with in the study of these diseases. When the presence 
of one or both kinds of bacteria has been positively determined, I find 
staining of very little value in subsequent work and simply examine 
fluids as described. When colonies are to be examined a drop of bouil- 
lon or water in which a trace of growth is stirred up is, of course, nec- 
essary. 

Another advantage of the bouillon and the condensation water of agar 
tubes rests upon the fsict that motile bacteria do not always become 
active at once when transferred from agar or gelatine into liquids for 
microscopical examination. Hence their motility may be entirely over- 
looked unless they are examined after having multiplied in liquids for 
some hours at least. 

It should likewise be borne in mind that the colonies of a few bacteria 
in a bit of tissue or drop of effusion from the diseased body may escape 
attention on a plate when many other colonies are present, and that 
they may be entirely lost on the second or third plate. In bouillon, 
however, both kinds of bacteria have for a time the same opportunities 
for multiplication, and both may be detected on the following day, 
though there may have been originally a great difference in the num- 
bers introduced. While agar plates have occasionally failed to dem- 
onstrate the presence of certain bacteria, owing either to a failure to 
multiply or to the rapid growth of other bacteria, or to rapid drying out 
of the agar layer, bouillon and agar tube cultures made at the same 
time have furnished the desired information. 

In order to detect both kinds of bacteria it is therefore essential that 
bouillon and inclined agar in tubes be used with agar plates. The 
method pursued in the investigations detailed in full in this report was 
always to prepare plates from lungs. When there was no time for the 
preparation of plates from other organs, such as spleen, liver, and kid- 
neys, tubes of bouillon and agar were used in i^lace of them, and, if 
necessary, plates were prepared from these. 

A minor diificulty, but one which may prove of more serious conse- 
quence to beginners, is the frequent encountering of bacteria other 
than those producing the disease in the organs of diseased swine. A 
perusal of the bacteriological observations in this report will show how 
much time has to be spent in isolating these bacteria and deter min- 

* See Special Kei)ort ou Hog Cliolera, 1889, for the characters of these bacilli. 



16 

ing what relation they bear to the disease. Many of them can event- 
ually be traced to the intestines where they commonly vegetate. Their 
presence in the internal organs may be accounted for by the extensive 
lesions in lungs and intestines which serve as entrances into the blood. 
This presence of strange bacteria has also been observed in other infec- 
tious diseases by other observers, and attention has been called to it in 
connection with hog cholera in the special report on that malady, p. 58. 

The detection of these foreign bacteria has been in large part due to 
the use of bouillon. As they are usually present in very small numbers 
their colonies on plates might easily be overlooked or attributed to 
accidental infection. They would appear only on the first plate among 
large numbers of other colonies and most likely be overlooked, since 
the development of colonies on crowded plates is limited, and they fre- 
quently fail to show any special features unless they have time and 
opportunity to expand. This is true of gelatine and particularly so of 
agar, on which colonies show, at best, few differences. When bouillon 
is inoculated all bacteria have for a time equal opportunities to develop, 
as stated above, and they at once thrust themselves upon our attention. 
Such mixed cultures have been and are still styled contaminated by 
those who fail to see their real significance. Such criticisms may, 
however, be safely left to take care of themselves at the present time. 

As an illustration of the foregoing, I have frequently found in the bot- 
tom of bouillon tubes into which a bit of tissue had been introduced 
large spore-bearing bacilli, which have been referred to in the various 
reports as "anaerobic," "post-mortem" bacilli. These bacilli do not 
develop in fresh cultures, nor would they appear on plates. The bot- 
tom of the culture liquid and the bit of tissue furnish for the time a 
suitable soil.* 

The use of animals in the isolation of bacteria is of great value in 
swine diseases. Babbits are peculiarly susceptible to swine-plague bac- 
teria. Inoculated with the more virulent varieties they die within 20 
hours, and the inoculated bacteria can be obtained from the various 
organs. Frequently when cultures failed to determine the presence of 
these bacteria in tissues rabbit inoculation was still successful. When 
a mixed outbreak is under examination it is evident that since rabbits 
do not succumb to minute doses of hog-cholera bacilli in less than 7 
days, the rabbits will die of swine plague first and the hog-cholera 
bacilli will not be obtained from their organs. There are, however, at- 
tenuated varieties of swine-plague bacteria frequently encountered in 
mixed outbreaks which j)rove fatal to rabbits in from 3 to 10 days. In 
these cases when pure cultures are inoculated there is more or less sup- 
purative destruction of the subcutis starting from the point of inoc- 
ulation, while the internal organs are quite free from changes and 
bacteria also. In such protracted cases, provided both kinds of bacte- 

* For a simple method of cultivatiug auch bacteria in addition to those now in use 
for anaerobes, see foot-note, p. 81. 



17 

ria were originally present in the tissue inoculated, both kinds ma^y ap- 
pear in the rabbit cultures, or only the hoj^-cliolera bacilli may have 
become disseminated through the body, while the swine-plague bacteria 
may be limited to the inoculated locality. Since hog-cholera bacilli do 
not produce much local iiiHaimnation, whenever this is extensive in 
rabbits inoculated directly from the pig, it is pretty certain that swine- 
plague bacteria and perhaps other still unknown bacteria may have 
caused it aiul should be looked for. 

Eabbit inoculation may thus prove very serviceable, but the post- 
mortem appearances must be carefully interpreted in connection with 
the bacteriological observations. In any case they rarely bring to light 
hog-cholera bacilli when the inoculated animal succumbs to swine plague 
before the fourth or fifth day. 

A few words are necessarj^ to define some of the anatomical terms 
used in the autopsy notes, inasmuch as a thorough description of the 
visceral anatomy of the domesticated animals has not yet been made. 
Since the lesions are confined chiefly to the lungs and intestines our 
remarks will be confined to these organs. 

When inflated through the trachea after the sternum is removed, and while the Iniigs 
are still in their natural position in the thoracic cavity, it will he ohserved that the 
surface resting against the ribs laterally is the most extensive. That surface rest- 
ing upon the diaphragm comes next, while the ventral aspect is the smallest. (See 
Plates I, II.) The right lung is made up of four lobes, the left has only three. (In 
text-books on anatomy the left lung is considered as being made up of only two.) 

In both there is a large principal lobe resting ui)on the diaphragm and against the 
adjacent thoracic wall. This lobe forms the major part of each lung. The remainder 
occupying the anterior (or cephalic) portion of the cavity, is made up of two small 
lobes, one extending ventrally (or downward in the standing position of the animal) 
and in the expanded state covering the heart laterally, the other extending towards 
the head and overlapping the base of the heart. These small lobes may be denomi- 
nated the ventral and cephalic lobes, respectively. The right cephalic lobe is lonoer 
and more distinct from the ventral lobe than the corresponding left cephalic. 
Wedged in between the two principal lobes and resting on the diaphragm is a small 
lobe, pyramidal, belonging to the right lung (azygos or median lobe). This lobe rests 
on the left, against the mediastinal membrane, and on the right it is separated from 
the right principal lobe by a fold of the pleura jiassing from the ventral thoracic wall 
to inclose the inferior vena cava. This small lobe is almost completely shut off, there- 
fore, from the other lobes by folds of the pleura. 

When the trachea and its branches have been examined it is easier to understand 
this division into lobes. The trachea divides in the thorax into two principal 
branches or bronchi. These bronchi pass into the principal lobes, straight to 
the caudal border, giving otf a number of small branches along their course. Very 
near the place of bifurcation the left bronchus gives off a large branch, which rami- 
fies in the substance of the left ventral lobe. From this branch another goes to the 
cephalic lobe. In some lungs the branches of these two lobes arise together from a 
very short, scarcely perceptible trunk, and are of nearly equal size. The bronchial 
supply of the right lung differs materially from that of the left. About 2 centimetres 
from the bifurcation the trachea gives off a small bronchus, which supplies the right 
cephalic lobe exclusively. At the bifurcation the right bronchus sends a short 
branch to the small median or azygos lobe and one to the ventral lobe. 

The major portion of the large intestine of the pig consists of a duplicature which 
1614 2 



18 

is coilerl upon itself somewhat like a watch spring. The cpecum is bonud down to 
the dorsal wall of the abdominal cavity on the right side. Similarly the rectum aud 
a small portion of adjacent colon is fastened down by peritoneal folds. If, starting 
from ca-cum and rectum as fixed points, the entire large intestiue be folded on itself 
at the middle point of its length aud the whole coiled up, beginning at this point as 
the free central end, we have imitated the general arrangement of the large intestine 
in the abdomen. The coiled part is loosely bound together and readily movable in 
the abdomen. As regards the dimensious the following measurements are taken from 
a male pig about 7 mouths old, and 3i) inches long from the tip of snout to root of tail. 
The intestine was distented with normal feces : 1, Ciecum, extending from closed end 
to ileo-ca3cal valve, 7^ inches long ; 2, from valve to duplicature or bend in the center 
of the coil, 5 feet ; 3, from the latter point to anus, 6 feet. It will be noticed that the 
folding takes place in the middle of the entire length of the large intestine. 

In the description of the regions the duplicature is a convenient point at which to 
distinguish the upper from the lower colon. Where tlie rectum begins it would be diffi- 
cult to determine without careful anatomical observations. Provisionally, its limit 
if determined by its old original signification maybe placed at eight to twelve inches 
from the external opening or anus. 

In examining the large intestiue it is best to begin the separation at the fold or 
bend in the center of the coil and continue until the c»cum and lower colon are 
reached. The c;ecum is easily removed with the small intestine attached. The lower 
colon is associated with the duodenum in the same mesentery and is crossed by it. 
Care must be taken not to injure either tube at this point in attempting to separate 
them. In beginning it is best to tie a string around the tube at the flexure as a 
landmark for future reference. 

The writer has used, apparently without discrimination, the English 
aud the metric system of weights aud measures. It will be noticed, 
however, that in the more strictly scientific part of the work only the 
metric system is used, while in those portions which may be interestiug 
to a wider circle the English system is substituted. 



BRIEF SUMMARY OF EARLIER INVESTIGATIONS— i886-'88. 



I. 

During the summer of 188G the writer made a number of post-mortem 
examinations of diseased pigs in Illinois,! for the purpose of identifying, 
if possible, the swine diseases existing in the Western States with the 
disease of hog cholera (or swine plague as it was then denominated), 
under observation since November, 1885, on the Experiment Station 
near Washington. It will be remembered that the hog-cholera bacillus 
was discovered in November of 1885, and carefully studied as to its 
morphological and pathogenic characters. 

The post-mortem examinations were made in the field, the spleen 
removed, placed in a sterilized bottle, and the cultures made either im- 
mediately or several hours later, indoors. During the first visit to 
Illinois in July, 1886, pigs were examined in Marion, Champaign, and 
Henry Counties. In some cases the lungs were diseased. In most cases 
the intestines were more or less ecchymosed, while ulcers or indurations 
of the mucous membrane were rare. What was most surprising, how- 
ever, was the absence of any bacteria in the spleen of seven out of 
eight animals examined. In the eighth case there was considerable 
pneumonia associated with pigmentation of the mucosa in the large 
intestines. The culture from the spleen contained two species of bac- 
teria, the bacillus coli communis, a common inhabitant of the digestive 
tract of the pig and other domesticated animals, and a small, non-motile 
bacterium which possessed pathogenic properties as the inoculations 
made at that time distinctly demonstrated. These bacteria were isolated 
by inoculating a rabbit subcutaneously with a bouillon culture contain- 
ing both kinds of bacteria. The rabbit died in 7 days with exten- 
sive inflammation of the subcutaneous tissue starting from the point of 
inoculation. Cultures from the spleen, liver, and blood contained onl^^ 
one form, the oval non-motile bacterium. A second rabbit, which re- 
ceived one-sixth cubic centimetre of a pure bouillon culture of these 
bacteria under the skin, died in 3 days with beginning peritonitis. Two 
mice, inoculated in the same manner, died respectively 1 and 2 days after 
inoculation. 

'Already published in detail in various reports of the DeiJartmcnt of Agriculture. 
tSee Rei)ort of the Bureau of Animal Industry for 1886, p. 76. 

19 



20 

Much time was spent in studying tlie motile bacillus, owing to its 
superficial resemblance to hog-cholera bacilli. Any one familiar with 
intestinal bacteria will, I think, at once concede, after reading the de- 
scription on page 78 of the report referred to, that this was the bacillus 
coli. The peculiar expanding and rapid groM th on gelatine, the coagu- 
lation of milk, the offensive, putrescent odor of the cultures, are prop- 
erties which do not belong to hog cholera bacilli. ' Moreover there was 
no manifestation of any pathogenic power. The small non-motile 
bacteria were identical with those named throughout this report as 
swine-plague bacteria. 

II. 

Several months later the writer, having found the information ob- 
tained on this journey quite different from what was expected, under- 
took another journey in the same State.* As usual the various re- 
ports of swine disease found in the papers vanished before the writer's 
approach, and after much search a herd was found near Sodorus, 
Champaign County, in which a number of animals had already perished 
and some were very sick. Two of the latter were killed. In Ko. 1 
there were extensive pneumonia and some large ulcers in the large in- 
testine. In No. 2 there were the same pneumonia, a very large spleen, 
and one ulcer on the valve in the large intestine. Various cultures 
were made at the time and blood was collected in pipettes which were 
sealed in the flame. The result of the bacteriological examination was 
briefly as follows: 

From No. 1: The spleen contained only hog- cholera bacteria. The 
blood (first pipette) hog-cholera bacteria and streptococci. The blood 
(second pipette) contained only swine-plague bacteria. 

From No. 2: The spleen, blood, and pleural cavity each contained 
swine-plague bacteria. 

Sections of the luog tissue of No. 2, hardened in alcohol, showed large 
numbers of swine-plague bacteria in the alveoli. 

With swine-plague bacteria from the pleural tube cultures of pig No. 
2 a considerable number of inoculations were made upon smaller ani- 
mals to determine their pathogenic power as compared with the swine- 
plague bacteria already found. The inoculations were made by inject- 
ing definite quantities of bouillon cultures which had been inoculated 
from single colonies on gelatine plates. 

One mouse, one-eighth cubic centimetre subcutaneous! y, dies in 48 hours. 
One mouse, three-sixteenths cubic centimetre subcutaneously, dies in 24 hours. 
One mouse, one-twelfth cubic centimetre subcutaneously, dies in 2 days. 
One mouse, one-twelfth cubic centimetre subcutaneously, dies in 6 days. 

In these animals there were no marked lesions. In some the bacteria 
injected were present in large numbers in the various organs ; in others 
they were very scarce. 

*L. c, p. 79. 



21 

Oue rabbit, oue-eightb cubic centiraetro siibcutanooasly, dies in 4 days. 
One rabbit, oue-tburtii cubic centimetre subcutaueotisly, dies iu 5 days. 
Oue rabbit, oue-eiglith cubic ceutimetro subcutaueously, dies iu 3 days. 

In the rabbits at the place of iuoculation the subcutis was mncli 
thickened by i)nrnlent infiltration, and there was more or less hemor- 
rhagic and exudative peritonitis. In the exudate the injected bacteria 
were very abundant. 

Oue pigeon, one-half cubic centimetre subcutaneonsly, dies in 2 days. 
One pigeon, three-fourths cubic centimetre subcutaneously, dies iu 4 days. 

At the place of the inoculation the muscular tissue more or less 
necrosed. Bacteria not detected in the internal organs. 

One guiuea-pig, one-fourtlis cubic centimetre subcutaneously, dies in 6 days with 
slight local changes and exudative peritonitis and pleuritis. 

Oue fowl, one-half cubic centimetre subcutan(;onHly, dies in 5 days. 

Oue fowl, 1 cubic centimetre su1)cutaneously, recovered. 

In both there was extensive necrosis of the pectoral muscle at the place of inocu- 
lation. 

The following animals were inoculated by rubbing into the subcu- 
taneous tissue through an incision a loop dipped into a gelatine cul- 
ture : 

One guinea-pig (abdomen) dies iu 5 days; subcutaneous lesion very extensive. 

One guiuea-pig (abdomen) dies in 8 days; subcutaneous lesion very extensive. 

One mouse (root of tail) dies in 3 days. 

One mouse (root of tail) dies in 4 days. 

Oue rabbit (ear) dies in 9 days; extensive subcutaneous lesions. 

Two pigeons (breast) remain well. 

One fowl (breast) remains well. 

From cultures of the swine-plague bacteria derived from the blood 
of pig Xo. 1 two rabbits were inoculated to see if the bacteria from 
both cases were identical. 

One rabbit received one twenty-fourth cubic centimetre bouillon culture; died in 
3 days. 

One rabbit received a loop of gelatine culture; died in 10 days. 

In both there was much local inflammation in the subcutis and peritonitis. 

With cultures of the swine-plague bacteria from these two sources a 
number of pigs were inoculated as indicated in the table : 



Pigs. 


Dale of in- 
oculation. 


Quantity 
injected. 


Soui'ce of culture. 


Eemarks. 


No 287 


Sept. 11, 1886 

do 

Oct. 30,1880 

....do 

Oct. 4, 1886 

fin 


c. c. 

*5 

*5" 

*3 

*5 

4* 

*5 




Dies in 18 days. 

Dies in 10 days; generalized jaundice. 

Dies in 58 daya. 


No 2H9 


....do 


No 30:t 


....do 


No 367 


do 


No 330 


Sodoi US, 111 


Dies in 9 days ; jaundice. 

Dies iu 35 days. 

Dies in 8 days ; jaundice. 

No effect. 

Dies in 11 days ; jaundice. 

Dies in 7 days ; jaundice. 


No 331 


....do 


No 364 Opt. so IRRfi 


do 


No. 366 
No. 374 
No. 375 


....do 

Nov. 18, 1886 
...do 


....do 

....do 

...do 



* Subcutaneous. 



tinto right lung. 



22 

It will be seen that of these ten pigs eight were inoculated subcu- 
taneously with doses ranging from 2J to 5 cubic centimetres of a bouil- 
lon culture. Two died from 1 to 2 months after inoculation, the remain- 
ing six in from 7 to 18 days thereafter with a x>eculiar disease of the 
liver and generalized jaundice. 

Two inoculated into the lung tissue through the right chest wall re- 
mained unaffected. 

The liver in these cases was greatly enlarged and so firm that when 
removed from the bodj' there was no change of form. There was no 
obstruction to the flow of bile in the bile ducts. The disease of the 
liver tissue itself was shown in sections of cases 289 and 375 to be due 
to inflammatory foci within the lobules. In some of these foci the pa- 
renchyma cells were still visible, but very feebly stained ; the trabecular 
arrangement was destroyed j the nuclei of the cells very much shriveled 
or absent. In other foci the i)arenchyma was replaced by numerous 
round cells. From these observations it would seem that the disease 
consisted of necrosis of a mass of hepatic cells followed by round cell 
infiltration. These foci varied in size from one-eighth to one-half the 
area of the lobule. Almost every lobule was affected, either several 
small areas or one large area of disease being present in each, situated 
usually near the periphery. In No. 375 there was also very extensive 
cellular infiltration beneath the capsule.* 

That the disease was induced by the inoculation can not be very well 
denied in view of the facts in the case. The animals used were from 
four difl'erent lots purchased from four diflerent owners.t No other 
animal in these lots died with these lesions of the liver. The inocula- 
tions must, therefore, be considered as the direct cause of the fatal 
result. 

These experiments are in so far remarkable as future subcutaneous 
inoculations with swine-plague bacteria from other sources, with one 
exception, produced no effect. 1 have not observed this disease. since 
the time these experiments were made. The only explanation which 
can be made is that these varieties of swine-plague bacteria had a 
slightly different pathogenic power which manifested itself in the man- 
ner described. 

* Much ill-considered criticism has beeu leveled at these expcrimeuts and results 
by F. S. Billings, and they are, therefore, presented again simply to show the im- 
fouuded character of these criticisms. While the term cirrhosis used in the earlier 
reports may not have exactly expressed the diseased condition of the liver, it should 
also be remembered that the held of comparative patliology is not sufficiently devel- 
oped to aid us in choosing terms or in finding certain diseases already described and 
named. 

tNos. 287-294, bought June 1, 1886, when 8 weeks old, from Mr. M. ; Nos. 329-335, 
bought Aug. 27, 1886, when 8 weeks old. from Mr. B. ; Nos. 303-367, bought Oct. 18, 
1886, when 8 weeks old, from Mr. J. ; Nos. 368-382, bought Oct. 18, 1886, when 8 
weeks old, from Mr. J. F. 



23 



TIL 

Toward the close of 1880* Dr. Paaren sent to the Bureau portions of 
lungs from Oerro Gordo Oounty, Iowa, These i)ortions indicated con- 
solidation of the lung tissue with necrotic foci and exudative pleuritis. 
By inoculation into mice and rabbits swine-plague bacteria were ob- 
tained, which, reinocnlated in pure culture, produced death within 24 
hours. The bacteria, very abundant in the internal organs, showed 
distinctly the polar stain. f They did not diUer in any respect from the 
bacteria found in Illinois, excepting in their greater virulence on the 
smaller experimental animals. Two pigs inoculated subcutaneously 
with' 5 cubic centimetres each did not manifest any signs of disease. 

IV. 

In February of 1887 an outbreak of swine disease came under obser- 
vation which showed conclusively the transmissibility of the lung dis- 
ease and the bacteria which are the cause. 

The disease was associated in every case with pneumonia and pleuritis 
of a more or less severe character. In the course of the disease casea- 
tion of the involved lung tissue was frequently observed. Intestinal 
lesions of a kind hitherto observed but once before^ were present in the 
earlier cases. These investigations have been criticised by F. S. Bil- 
lings, if his statements deserve the name of criticism, because, in addi- 
tion to the swine-plague bacteria found in almost every case, hog-cholera 
bacilli were detected in the later cases. It is difficult to discover from 
his statements which of the two bacteria he objects to. His own report 
leaves us wholly in the dark which kind he himself has found in Ne- 
braska, owing to the ambiguous manner in which the bacteria found by 
him have been described. We may therefore pass over these criticisms 
and briefly summarize the investigations§ which have since been con- 
firmed by much more extended ones. 

On January 31 a small number of pigs were purchased from a farm 
adjoining the Experiment Station for the purpose of testing the effect 
of different cathartics on the healthy pig. The animals had been pur- 
chased from this farm because no disease had existed there for several 
years. These pigs (Nos. 402-406, inclusive) were put in a pen by them- 
selves. On the following day one (No. 400) was found dead with exten- 
sive ulceration of the large intestine, but no lung disease. This occur- 
rence of course spoiled the entire experiment as i^lanned. The disease 
was regarded as hog cholera by me, although I did not examine the 

*L,c.,p.92. 

t For the meaniug of tliis expression, see p. 85. 
t Report of the Bureau for 1886, p. 06. 

sS For a full account of the autopsy notes and bacteriological examination, see report 
of the Bureau for 1887, p. 86. 



24 

animal or make cultures, being engaged in other work at the time. An- 
other fact which led to the supposition that this disease was different 
from the disease which appeared later in the other animals of this lot 
was told by the owner. Nos. 405 and 406 were the only pigs which had 
not been confined in pens, and which, therefore, may have been ex- 
posed to infection on the farm which did not reach the i^enned animals. 
At the time No. 400 died (February 1), the other animals appeared 
well. Some of these were distributed into small pens by themselves 
and fed different doses of cathartics. Meanwhile no other animal of 
this lot died until 15 days later, when 403 died. The following table 
gives information concerning the rest: 



Pigs. 



No. 406 
No. 403 
No. 405 
No. 402 
No. 404 



Date of 
death. 



Remarks. 



Feb. 1 ] Intestinal ulcers. 

Feb. 16. .. Veutral lobes of liiiifrs diseased : croupous iuflamiiiatiou of large intestine. 
Feb. 18- .. Extensive pneumonia and pleuriiis ; croupous inflammation of large intestine. 
Feb. 19 .. Slight pneumonia ; croupous inflammation of large intestine. 
Not afl'ected. 



As regards the bacteriological examination the following may be said : 

No. 406. None made because disease supposed to be hog cholera. 
No. 403. None made for same reasoQ. 

No. 405. Swine-plague bacteria found in lungs; other organs not examined. 
No. 402. Bouillon cultures made from pleural shreds, spleen, liver, and blood. 
Gelatine cultures made from blood and liver. 

Nearly all the cultures from No. 402 contained a large spore-bearing 
bacillus which I have frequently found since then in cases of swine dis- 
ease having hemorrhagic lesions. Cultures from the liver and blood 
contained also swine-plague bacteria which were isolated by rabbit 
inoculation. 

It will be noticed that in the later cases, Nos. 403, 405, and 402, the 
large intestine was the seat of a peculiarly intense inflammation, ac- 
companied by the exudation of circumscribed masses of fibrin easily 
lifted away from the mucosa, leaving a paler, slightly depressed spot 
showing no necrosis of tissue. In the rectum this exudate formed a 
continuous sheet also easily removable. 

It might be claimed that the feeding of a dose of aloes or salts may 
have caused this peculiar intestinal inflammation. This claim, however, 
is effectually disposed of by case No. 407. This animal, one of the same 
herd, had not been taken from the neighboring farm. It was found 
dead February 22, and brought to the Station for examination. The 
notes of this case are reproduced because it must be considered the 
most trustworthy of all. 

No. 407. Pig of medium size, white ; skin of abdomen, chest, neck, and back deeply 
reddened. Fat abundant, slightly reddened along" the linea alba. Superficial 
inguinal glands slightly enlarged ; spleen dotted with elevated blood-red points.* 

* These points are found in .spleens of healthy swine. 



25 

stomach ami (liiodouum uormal, tlio latter bile-staiuod. In ileiiiii Pcyor's patches 
are visible as <froai»s of small, dark dots ; uo swelling. Mucosa of c;ecam and upper 
colon of a dirty blackish color, probably pigmented. A few hajmatomata beneath 
mucosa. Besides the ditt'use pigmentation the mucosa is siiriukled with isolated or 
conflueut masses, about one-eighth to one-fourth inch in diameter, of a dirty grayish- 
yellow color, loosely adherent to the membrane. When pulled away a slightly 
depressed surface is exposed. Much of this mass can bo easily removed by simply 
moving the scalpel over it. There are several ulcers in the caicum with decided loss 
of substance. The patch of mucous glands at the base of the valve is also converted 
into an ulcerated mass. Lymphatic glands in abdomen slightly swollen and red- 
dened. Kidneys deeply reddened to tips of papillic. 

On opening the thorax the lungs did not collapse, and a rather disagreeable odor 
was perceived. As in No. 405, the ventral and cephalic lobes of both lungs were 
consolidated. The hepatized regions were very hard to the touch, bright red, with 
yellowish points sprinkled in regularly. (See Plates III and iv.) The right lung- 
was adherent to chest wall over the hepatized portion. A whitish, spongy mem- 
brane was interposed, about one-eighth to one-fourth inch thick, inclosing a small 
quantity of turbid liquid. Ou removing the lungs the membrane remained adherent 
to the pulmonary pleura, and was removed with difficulty. A portion of the dia- 
phragm was also firmly attached. The left lung adhered firmly to the chest wall in 
two places, where it was consolidated. The costal pleura was deeply reddened, 
owing to the injection of a close net-work of minute vessels. Trachea and bronchi 
filled with whitish foam. 

On section, the consolidated region is sharply but irregularly marked off from the 
normal tissue, very consistent and slightly elevated. The color varies from a bright 
red to a grayish red. In all, minute grayish points are present one-twelfth inch in 
diameter, about the same distance apart, and of a hazy outline. The smaller bronchi 
are filled with a purulent fiuid. In the surrounding lobules in which the disease is 
more advanced the interlobular tissue is distended with a serous infiltration ; the 
large vessels are filled with very consistent dark clots. Heart rather large, pericar- 
dium free ; right auricle, ventricle, and large veins distended with clots ; small 
white clot in left ventricle. 

Microscopic examination of the lung tissue in cover-glass preparations shows the 
presence of numerous bacteria with the polar stain in recent lesions ; in older ones 
they are rare. Other forms are ijresent, but only in small numbers. The pleural 
exudate was made up of rounds cells, bound together by bundles of fibrin ; it con- 
tains few bacteria. 

lu transverse sections of the large intestine, where a mass of exudate is still 
attached, the muscular and submucous layers are intact, if we except a slight cellu- 
lar infiltration near the base of the crypts. The mucous layer, however, is consider- 
ably changed. The surface epithelium, including a portion of the crypts of Lieber- 
kiihn, is no longer distinguishable, but merges without demarcation iuto an exudate 
several millimetres thick, consisting of leucocytes imbedded in a mesh- work of fibrin, 
the whole refusing to stain. 

Pure cultures of swine-plague bacteria in tubes of gelatine were obtained from the 
pleural exudate. In each needle track a large number of colonies developed. A 
piece of false membrane gave the same result. Cover-glass preparations from spleen 
and liver were negative. Two tubes of beef infusion into which bits of spleen had 
been dropped remained sterile. Two similar cultures from the liver contained each 
a large bacillus, evidently of post-mortem growth. The blood from the heart was 
also free from bacteria, for two tubes of gelatine, each inoculated six or seven times 
with blood, did not develop a single colony. 

A rabbit inoculated in the ear with a bit of lung tissue died within 4 days. There 
was no swelling or reddening of the ear. Lungs deeply congested (hypostatic?). 
Immense numbers of swine-plague bacteria in blood, spleen, and liver. Cultures 



26 

from blood and liver contained the same organisms. A mouse inoculated with a 
bit of lung tissue succumbed within 2 days. Bacteria very scarce in body. Pure 
cultures of swine-plague bacteria were, however, obtained from heart's blood. 

What is of importance in tliis case and in No. 402 is the absence of 
hog-cholera bacilli from the internal organs where we wonld certainly 
expect to find them in this disease. If wo refuse to consider the intes- 
tinal lesions as caused by swine-plague bacteria, we have the alter- 
native of assuming the existence of bacteria which produce intestinal 
disease without penetrating into the internal organs proper.* 

Five other cases in this investigation deserve special attention. N'os. 
408, 409, and 410 of the same herd still remained on the farm. After 
the examination of 407 had shown the absence of hog cholera, and the 
presence in the diseased lungs of swine-plague germs, and the evidence 
thus far obtained pointed to a different disease caused by the latter 
bacteria, two pigs, Nos. 359 and 360, were taken from the Station to the 
farm and penned with the three mentioned to determine whether the 
disease is readily communicable. This was done February 28. March 
5, No. 408 died. March IG the remaining four were taken back to the 
Station and placed in an unused pen free from infection, so as to be 
under observation. 

Of these four pigs No. 409 died March 20, No. 410, March 29. Of the 
exposed animals No. 359 died March 24, 24 days after the commence- 
ment of the exposure ; No. 360, April 6, 37 days thereafter. Of these 
four cases No. 360 was not examined. Of the remaining three, hog- 
cholera bacilli were detected in 409 by rabbit inoculation, but not in 
either 408 or 410, while swine-plague bacteria were found in 408 and 
359. Looking over the original notes I am convinced that the number 
of cultures made from the spleens of 408, 410, and 359 were suflBcient to 
enable us to exclude the presence of hog cholera from these cases. No. 
409 is therefore the only animal from the adjoining farm which was ex- 
amined in which hog-cholera bacilli were detected. It is likewise 
strange that in the spleen of No. 408 a bacillus should appear resem- 
bling hog-cholera bacillus in many respects, but not identical with it, 
and producing only supi^uration in rabbits. 

The cases which came under observation subsequently, and in which 
hog-cholera bacilli were readily demonstrated in the spleen, were Station 
pigs which had been exposed some time ago to the infection of hog 
cholera. These cases are chiefly valuable in pointing out that the swine- 
plague bacteria are transmitted from animal to animal and associated 
with lung disease. They may be thrown out altogether, since the 
source of the hog-cholera bacilli is traceable. 

No. 372. Fed viscera of hog cholera case December 24, 1886, in infected 
pen. 

* By " internal organs " I mean those organs which db not come in contact with the 
air or food, either directly or indirectly. Thus the entire respiratory and digestive 
tract may be regarded as external, so far as bacteria are concerned. 



27 

No. 378. Fed viscera of hog cholera case Ifovember 18, 188<>, in in- 
fected pen. Fed viscera of 406 Febrnary 2, in infe(;ted pen. 

No. 3913. Inocnlated with swine plague bacteria (Iowa) January 25; 
placed in the infected pen March 28. 

No. 397. Fed viscera of 378 in pen 7 March 24. 

In 372, 392, 397, both hog cholera and swine plague bacteria were 
found. Their presence in the old infected pen or their contact with 
pigs kept there will account for this double infection. 

The facts brought out by this investigation corroborated those al- 
ready brought out in the investigations of the preceding year. They 
showed the existence of pneumonia and pleuritis, together with intesti- 
nal disease in most of the animals examined, associated with bacteria 
readily distinguished from hog-cholera bacteria. 

They also demonstrated the trausmissibility of the pneumonia to other 
pigs, and in these pigs the same bacteria were found. 

If the lesions of the large intestine, as observed in the early cases, 
were due to hog-cholera bacilli, why were these bacilli not found ex- 
cepting in one late case in which there may have been an accidental 
infection of the rabbit inoculated ? Why were hog-cholera bacilli read- 
ily detected in the later cases kept in the infected pen ? 

While these investigations do not prove that the swine-plague bac- 
teria were the cause of the intestinal lesions, they also do not seem to 
show any relationship between these lesions and hog-cholera bacilli. 
This question of the relation between intestinal lesions and swine- 
plague bacteria will be discussed farther on.* 

V. 

In September, 1888, an outbreak of swine disease near Baltimore, 
Md., came to our notice. Throe pigs from one herd and one from another 
herd were examined. The following syno])sis of the cases may be of 
interest, the full account being given elsewhere. t 

Pig No. 1. Broncho-pneumonia; exudate on mucosa of rectum and 
lower colon ; swine-plague bacteria detected in lungs and rectum ; hog- 
cholera bacilli in si)leen. 

Pig No. 2: Three-quarters of both lungs hepatized ; ulcers in ileum 
and colon; swine-plague bacteria in lungs; hog-cholera bacteria in 
spleen. 

Pig No. 3: Extensive pneumonia and pleurisy; ulceration of large 
intestine; swine-plague bacteria in lungs; hog cholera bacteria in spleen. 

Pig No. 4 : Slight atelectasis of lungs ; ulcers in large intestine ; 
swine-plague bacteria in large intestine; hog-cholera bacteria in spleen. 

Pig No. 3 was taken to the Experiment Station, where it became the 
starting point of a mixed outbreak of hog cholera and pneumonia. 

* P. 102. 

t Report of the Bureau, etc., 1887-'88, p. 121. 



28 



VI. 

Duriag iJ^ovember, 1888, the writer was directed to make some in- 
vestigations in Iowa,* where swine diseases at that time were prevail- 
ing to a considerable extent. In the vicinity of Mason City pigs from 
three herds, some distance apart, were examined. The lesions observed 
were both intestinal and pulmonary. The intestinal lesions, though 
varying considerably in appearance and intensity, did not differ, on the 
whole, from those observed in hog cholera. The lung lesions varied 
considerably in character and extent, from a slight collapse in a single 
lobe to almost total hepatization, accompanied by exudative pleuritis. 

The investigations were limited to post mortem examination and 
cultures from the spleen. From each spleen small bits of tissue were 
removed to two tubes of agar. In addition, portions of diseased lung 
tissue and ulcerated mucous membrane from the large intestine were cut 
out and transferred to sterile test tubes plugged with cotton wool for 
inoculation into rabbits. Ten pigs were examined in this manner. 

In but one case did the spleen pulp show any bacteria under the 
microscope, and in this case they were streptococci, tn but one agar 
tube of the spleen series did anything develop. This was a motile 
bacillus, resembling the hog cholera bacillus in form, but differing in 
its growth on agar, in bouillon, and in gelatine, this growth being in 
all cases more vigorous. Of two mice and one rabbit inoculated, one 
mouse died in 5 days. The lesions were indefinite and did not point 
to hog cholera. Moreover, the other mouse and the rabbit remained 
unafiected. 

With particles of diseased lung tissue and mucous membrane from 
some of these cases a considerable number of rabbits and some mice 
were inoculated. Of those that died some contained no bacteria of any 
description. Those inoculated from three cases out of ten died of 
swine plague since these bacteria were found. A few survived the 
inoculation. 

The nature of this disease was not, therefore, cleared up by these in- 
vestigations, since the results were not uniform. While in hog chol- 
era the bacilli are present in the spleen, and readily obtained therefrom 
by cultivation, they were not present in the spleens of these ten cases. 
As already stated, swine-plague bacteria were obtained from three cases. 
They were quite virulent, as the inoculations upon pigs show. Thus 
one pig, which received 9 cubic centimetres of a bouillon culture into 
the right lung through the chest wall, died within 20 hours of septi- 
caemia, the injected bacteria being present in the spleen in considerable 
numbers. Another pig, which received a subcutaneous injection at the 
same time, remained well. Somewhat later two pigs received into the 
right lung 1^ cubic centimetres and 3 cubic centimetres of a bouillon 

* Report of the Bureau of Animal Industry for 1887-'88, pp. 135-145, wLore a de- 
tailed account of this work is given. 



29 

culture. The one which had received the smaller dose was sick for a 
time, but recovered. It was killed U months after the inoculation, and 
both lungs were found everywhere adherent to the chest wall. In the 
pericardial sac a considerable quantity of pus had collected, in which 
the injected bacteria were still present, as determined by cultures. 

The animal which had received the larger dose became very ill and 
was killed 5 days after inoculation. At the autopsy were detected par- 
tial hepatization of the right lung, with extensive exudative pleuritis 
and pericarditis. 

The two following cases, which have not yet been published, demon- 
strate very strikingly the virulence of these bacteria. The growth on 
a number of agar cultures about 9 days old was scraped off and trans- 
ferred to sterile bouillon until a turbid suspension was obtained. This 
suspension was prepared because these bacteria multiply very feebly 
in bouillon, and when the latter is used as the injecting fluid very few 
bacteria are actually introduced into the body. This turbid suspension 
was used to inoculate 2 pigs. No. 120 received into the abdomen 2 
cubic centimetres; No. 143 into the right lung through the chest wall 
but 1 cubic centimetre. The inoculation was made March 11, 1889, 
over 3 mouths after the bacteria had been obtained from the diseased 
swine. 

No. 120. Essex female, 5 months old. Into the right lung through the chest wall, 
2 cubic centimetres of above suspension injected with hypodermic syringe, 6 p. ra. 
March 11. Found dead early next morning. 

Subcutaneous inguinal glands partly hemorrhagic. From the cut subcutaneous 
vessels of right side liquid blood oozes out. In abdomen the solitary follicles of 
large intestine appear as bright red circular si^ots three-sixteenths inch diameter, as 
seen from serosa. Spleen slightly engorged. 

Large quantity of blood-stained serum iu right pleural sac. The needle had punc- 
tured the convex surface of principal lobe, where there was some infiltration of blood. 
A thin layer of fibrin on convex surface of the small anterior lobes and on pericardium. 
A few collapsed lobules along free border of these lobes. 

In stomach, the mucosa of fundus is deejily reddened over an area of 3 to 4 square 
inches; in this area two hemorrhagic spots. The npper half of duodenum with 
mucosa intensely reddened. Contents somewhat blood-stained. All Peyer's patches 
in the small intestine from duodenum to ileo-csecal valve are intensely reddened, 
the follicles appearing as blood-red points. On some patches, hemorrhages on the 
surface. Considerable number of ascarides in small intestine. In large intestine 
the lymphatic patch near valve likewise reddened. Mesenteric and mesocolic glands 
hyperajmic. 

Kidneys very much congested. The glomeruli appear as minute blood-red points. 
Small quantity of urine in bladder loaded with albumen. Blood fails to clot. Iu 
the spleen large numbers of swine plague bacteria. 

No. 143. Essex male, ,5 months old. Injected into abdomen 1 cubic centimetre of 
turbid suspension of swine plague bacteria, March 18. Animal dies 40 hours after 
inoculation. 

Inguinal glands slightly swollen and hyperamic. In abdominal cavity pe'ritoneum 
pale pink, all minute vessels injected. Shreds of a viscid grayish exudate attached 
to abdominal walls, contiguous coils of intestines, and stomach. Considerable opaque 
reddish serum present. Vessels of diaphragm injected; some ecchymoses observed. 
The shreddy exudate also present. The mesentery (Edematous, especially where 



30 

attached to intestines. The walls of a portion of the lower small intestine very 
mnch swollen, serosa dark red. On the mucosa which is congested a yellowish, 
pasty exudate loosely rests, occupying the side to which mesentery is attached. 
This exudate is made up of leucocytes imhedded in strands of fibrin. Peyer's patches 
along this region and down to ileo-cajcal valve are deeply congested and swollen so 
as to appear boat-shaped. (The bacteria had evidently traveled along mesentery 
and invaded the walls of the small intestine.) 

Large intestine distended with dry feces. Mucosa of caacum and colon more or 
less congested, the congestion limited mainly to summits of folds. The lymphatic 
patch near valve very hyperjemic and swollen. 

In each pleural sac about 50 cubic centimetres of reddish serum. A thin membra- 
nous exudate covering the dependent half of both lungs easily scraped away as a 
pale yellowish pulpy mass. The remainder of pleura opaque, a barely visible exu- 
date covt ring it. The lungs are hypersemic, the free border of the ventral and ce- 
phalic lobfts collapsed. Bronchial glands swollen and hyperjemic. 

Pericardium thickened, clouded ; vessels injected. A barely visible exudate on it. 
Vessels of heart surface very much distended. Petechia on left auricle and under 
endocardium of left ventricle near semi-lunar valves. Eight heart distended with a 
dark, soft coagulum. 

In the peritoneal exudate, which consists chiefly of fibrin and a few leucocytes, 
immense numbers of the injected bacteria are present, showing after staining the 
polar arrangement of protoplasm very distinctly. The pleural exudate composed of 
the same elements. In some leucocytes up to twenty bacteria. In the spleen and 
blood from the heart- laige numbers of swine-plague bacteria. Agar cultures from 
the spleen, pleural, and peritoneal cavities contain only the injected bacteria. A 
bouillon culture from the spleen likewise pure. 



INVESTIGATIONS OF i889-'90. 



The problem of swine diseases as it stood after the completion of 
these investigations up to 1889 may be stated briefly as follows: 

Since 1885 a well-characterized bacillus has been encountered as the 
cause of an infectious disease termed hog cholera, which is chiefly 
localized in the large intestine. Since 1886 our attention has been 
directed to lung disease in swine with which a bacterium is associated, 
which, when inoculated into swine, proves to be very virulent and may give 
rise to pneumonia when the bacteria are injected into the lungs. This 
is sufficient to demonstrate the existence of a disease differing from hog 
cholera, which has been called swine plague because an identical dis- 
ease of swine in Germany, first described in 1885, was called Scluveine- 
seuche. This lung disease was shown to be communicable. (IV.) * 

In many of the outbreaks examined the changes found in the intes- 
tines could not be distinguished from hog cholera (exce])t perhaps in 
lY). In some hog-cliolera bacilli were actually detected, in others 
(I, VI) they could not be found. One of the problems, therefore, still 
before us, and a very important one, was to determine whether all out- 
breaks of swine plague in wbich intestinal lesions closely resembling 
those of hog cholera are present are mixed outbreaks of swine plague 
and hog cholera, or are simply swine plague. 

Much light has been thrown upon this subject by the investigations of 
three outbreaks given in detail in the following pages. The first is a 
mixed outbreak in which, however, the lung lesions are so very well 
marked and the swine-plague bacteria associated with, these lesions so 
virulent that there can be little doubt that the hog cholera disease was 
really secondary to the swine plague. The second outbreak is simple, 
uncomplicated swine plague. In the third outbreak very virulent swine- 
plague bacteria, and, in one case, very attenuated hog-cholera bacilli 
were found. 

VII. 

An outbreak of swine disease appeared among the pigs belonging to 
an abattoir adjoining the Experiment Station about the first week in 
October, 1889. The disease came to our notice a week after the first 

* These nnmerals refer to the dilfereut outbreaks as unmbered iu this report. 

31 



32 

animals died, and in attempting to trace the causes which led to it we 
obtained the following information : 

The pigs were purcliased in the markets of Washington City the lat- 
ter part of September. They were thirty-five in number, in two, possi- 
bly three, lots. One lot came in two crates. It could not be deter- 
mined whether it was made up of pigs from one or two sources. They 
began to die, as stated, about a week after their arrival. We examined 
in all thirteen animals, the first on October 12, the last on October 28. 
A few days later the last of these thirty-five pigs succumbed to the dis- 
ease. It lasted, therefore, about 1 month. A few large swine which 
were on the place when these animals arrived did not take the infection. 

In the following pages a detailed statement of the pathological and 
the bacteriological examination is given. Those who are not specially 
interested in these notes will find a summary of the ascertained facts 
following them. 

No. 1. October 12. Male pig, weighing about 25 pounds, died last night. On inner 
aspect of right thigh an area, about one-half inch in diameter, of extravasation, ex- 
tending down into true skin. No ulcers in the mouth. Spleen not enlarged. 

Contents of stomach slight in amount, consisting chiefly of sand and a turbid 
liquid ; walls contracted, throwing mucosa into large folds. The greater part of 
mucosa intensely congested. In the fundus a large ulcer 1 i inches across, covered by 
a slough one-quarter inch thick. The subjacent wall nearly one-half inch thick, on 
section deeply reddened throughout, due to a sanguinolent, cedematous infiltration 
of the wall. Adjacent to this a smaller inflammatory thickening covered with a thin 
pultaceous slough. The mucosa of duodenum uniformly and deeply pigmented. In 
the ileum the mucosa is swollen, Peyer's patches reddened. 

Mucosa of cascum of a bluish-gray color, dotted with a small number of ulcers not 
much larger than pins' heads, covered with yellowish sloughs. Similar follicular 
ulcers on Peyer's patch near valve. Upper colon contains much earth, adhering rather 
closely to mucosa. The latter quite deeply pigmented, the pigmentation intensified 
in lower colon. In upper colon a small number of flattish yellowish-white sloughs 
from one-sixteenth to one-eighth inch in diameter. 

In thorax, the plenra covering the diaphragm and ribs is overlaid by a pale 
pinkish membranous exudate, easily rubbed off and especially abundant on the right 
side. 

The various lobes of both lungs firmly glued together by exudate. The ventral 
lobes, the major portion of cephalic lobes, and a small portion of the principal lobes 
adjacent to the ventrals are hepatized. The hepatized areas are covered by false 
membranes varying in thickness and easily peeled off. Through the hepatized lobes 
are disseminated necrotic masses of a greenish color varying in size from mere specks 
to peas. They contain large numbers of swine-plague bacteria, which show a polar 
stain very clearly. The tissue around the terminal portion of both bronchi in the 
principal lobes is hepatized and contains necrotic foci. Lung worms abundant in 
the left bronchus. Both bronchi contain small quantities of reddish foam. Peri- 
cardium thickened, opaque ; vessels injected ; the ventral surface is covered by a 
membranous exudate and it is adherent to the heart surface by means of a similar 
exudate. Cover-glass preparations from the pleural and pericardial exudate, from 
various regions of hepatized lung tissue, contain large numbers of swine-plague bac- 
teria. 

A rabbit was inoculated October 12, by placing a bit of lung tissue under the skin 
of abdomen. Dead next morning. Slight ecchymosis in the subcutis at the point 
of inoculation. The blood and spleen contain immense numbers of swine-plague 



33 

bacteria, sliowing well the polar arrauoeineiit of the protoplasm when stained. Cul- 
tures confirniatory, agar and bouillon being used chietly. 

A rabbit inoculated at the same time and in the same way with a bit of spleen 
tissue. Kabbit dead next morning. Swine plague bacteria fewer than in preceding 
case. An agar culture from the blood contains only those germs. From the spleen two 
agar, one bouillon, and one gelatine tube culture prepared. Ou the second day (Sun- 
day intervening) a moderate number of isolated colonies on the agar surfaces; the 
condensation water turbid with flaky deposits. In the bouillon tube are a large 
number of minute suspended flakes, the liquid itself not clouded. In these cultuies 
only swine-plague bacteria. The gelatine tube rcuuiined sterile. 

From the pleural exudate an agar and a bouillon tube were inoculated at the 
autopsy. On the second day a number of colonics similar to those on the spleen agar 
culture were found to be made up of swine-plague bacteria. The bouillon culture 
faintly and uniformly clouded. Only swine-plague germs present. From the epicar- 
dial exudate two similar cultures were prepared with the same result, with the ex- 
ception that in the bouillon culture large cocci were also present. 

With a bit of lung tissue taken from more recently diseased regions two gelatine 
rolls and two agar plates were made. In the second gelatine roll about 100 minute 
colonies present after 3 or 4 days. These were examined and bouillon tubes inocu- 
lated from four different colonies at different times. In all the swine-plague germs 
only appeared. The first agar plate developed a very large number of colonies, the 
second only six or seven, made up only of swiue-plague germs. 

No. 2. Female; died last night ; weighs about 35 i^onnds. Lymphatics in the groin 
barely enlarged, pale. Spleen quite large, softened, dark red in color. 

Digestive tract: Stomach x>artly filled with chewed leaves, and straw adhering 
slightly to mucosa. Fundus faintly reddened. The pyloric portion bile-stained. 
Duodenum similarly stained. An ascaris in the bile duct, projecting lA inches out 
into duodenum. Arborescent injection of mucosa of the latter. Considerable quan- 
tity of turbid liquid in large bowels. Mucosa not pigmented. Peyer's patch at base 
of valve thickened and pigmented. Ulcers moderately abundant in c;«cum and 
upper colon. They appear as little cup-shaped depressions, one-sixteenth to one- 
eighth inch in diameter,lined with a pale yellowish necrotic layer, the center in some 
filled with a black alough and the margin elevated. Mesenteric, mesocolic glands, 
and those of lesser omentum, slightly swollen ; cortical layer congested. Interlobu- 
lar markings of liver prominent, broadened. The section appears mottled, some lob- 
ules being much more congested than others. The empty gall-bladder contains a 
partly disintegrated ascaris, which extends through bile duct into duodenum. 

Thorax : The costal pleura of both sides highly injected and covered with a thin, 
whitish membranous exudate, gluing the lungs to the chest wall, ©f the lungs all 
but a small strip along the dorsal border of the principal lobes is solid, three or four 
times the size of the noruuil lung when collapsed. The various lobes are glued to 
each other, forming a single mass, in which the individual lobes ai'e not recognizable, 
and which is in turn attached to the chest wall, the diaphragm, and the pericardium 
by pleuritic exudate. This is most abundant, and forms membranes on the most de- 
pendent portions of the lungs, easily pulled away from the subjacent structures. The 
various adhesions torn without difficulty. 

The disease seems farthest advanced in the cephalic and ventral lobes, in which 
are imbedded a large number of closely set masses of dead tissue, from one-sixteenth 
to one-half inch in diameter. These are firm, yellowish masses, sharply detiued in 
outline, and imbedded in dark red hopatized tissue, which is mottled with paler 
speeks, representing the ultimate lobules distended with cell masses. 

The trachea and bronchi contain whitish foam, mixed with large quantities of 
thick, purulent secretion. In the bronchi of the principal lobes are many lung 
worms. The bronchial glands are hypenemic and O3demalous, and contain a small 
uum1)er of necrotic foci. 

1G14 3 



34 

In tlie spleen a few minute oval bacteria detected. With a platinum needle the 
surface of an agar tube and a bouillon tube inoculated. On following day the 
former showed a considerable number of round, grayish colonies, 1^ to 3 millimetres 
(one-sixteenth to one-eighth inch) in diameter; condensation water clouded. In this 
tube only swine-plague germs detected. The bouillon culture contains a considerable 
number of minute granules, representing clumps of swine-i^lague bacteria. 

An agar culture from the liver grew like the si)leen culture and contained only swine- 
plague germs. 

At the autopsy an agar and a bouillon tube inoculated from the right pleura. In 
the former only the condensation water became turbid and contaius swine-plague 
germs exclusively. The bouillon tube remains sterile; similarly a bouillon tube from 
pericardial exudate remains sterile. (It is highly probable that the flocculent growth 
of the swine-plague germs in bouillon and the sterility of these tubes was occasioned 
by an unsuitable condition of the bouillon.) 

From a bit of lung tissue, the pleural surface of which had been thoroughly 
scorched, gelatine roll cultures were prepared. After a number of days the first roll 
showed a large number of colonies as mere points, the second roll about 100 colonies, 
somewhat larger. From both tubes bouillon was inoculated from individual colonies, 
These contained after development only swine-plague bacteria. 

At the same time the scorched lung tissue was pricked with platinum needle and 
an agar tube inoculated. On the surface a considerable number of similar colonies 
appeared on the following day. Some of these examined were swine-plague germs. 
In the condensation water a few chains of a short, motionless rod appeared among 
the great bulk of swine-plague germs. 

At the same time a rabbit was inoculated from the lung tissue. It was dead next 
morning. Enormous numbers of polar stained swine-plague germs found in stained 
preparation of spleen pulp. An agar culture confirms the microscopic examination. 

No. 3. Died last night. Female ; weighs about 25 pounds; in very poor condition. 
Spleen considerably engorged ; contains a small number of bacteria ; nature to be 
determined by cultivation. 

Digestive tract : One ulcer on the gums of lower jaw. Stomach contents like 
those of No. 2. In the fundus an area of mucosa, about 4 inches in diameter, is nearly 
black from extravasation, and thickened. A zone several inches wide outside of this 
is deeply reddened. The mucosa of duodenum and ileum more or less discolored the 
vessels, showing arborescent injection. In the caicum, the mucosa is of a bluish- 
gray color, and dotted with a dozen sloughs, one-eighth inch diameter, of a yellow 
color; the tissue at the margin of the slough thickened, elevated. The Peyer's patch 
near valve deeply congested and sprinkled with enlarged grayish follicles. Mucosa 
of colon more OF less discolored and hyperoemic in patches; only three small ulcers 
found. The liver appears normal, the bile in bladder very thick, flaky. Punctiform 
ecchymoses on surface of kidneys. 

In the lungs the major portion of both ventral lobes is solidified, the tips being 
emphysematous. The hepatized jjortions are bright red in color, with faint yellow- 
ish mottling. 

Bacteriological examination : Cover-glass preparations of the hepatized lung tissue 
show no bacteria. From a bit of tissue two gelatine roll cultures prepared and a 
rabbit inoculated. Roll A subsequently contained a large number of apparently iden- 
tical colonies. Roll B, about fifty of the same colonies and one chromogene. Care- 
ful examination of these revealed hog-cholera bacilli. The inoculated rabbit died 
within 36 hours. At the place of inoculation the bit of lung tissue was surrounded 
by a small area of purulent infiltration and dilated blood-vessels. In the blood and 
spleen a very large number of swine-plague bacteria. A bouillon culture from the 
blood faintly clouded on the following day, and holding in suspension barely visible 
granules made up of cljimps of swine-plague bacteria. No motile bacteria detected. 

The spleen of the pj^ contained a few bacteria, character not determinable. With a^ 



35 

bit of pulp a gelatine roll A and agar plate B prepared. al«o a bouillon culture. The 
latter was uuifonuly clouded on the followiug day ; a few gas bubbles ou the snrface. 
Only motile hog-cholera bacteria present. The presence of hog-cholera baclli in the 
spleen was furthermore den>on«trated by the roll and plate culture. 1 ho agar plate 
grew, of course, most rapidly, being in the thermontat. On the second .ay a consul- 
trable number of colonies appeared, apparently the same. Examination of some 
showed only hog-cholera bacilli. A bouillon tube i.u.cuhited from one of them was 
clouded on the following day Avith motile hog-cholera bacilli. .. ^, , , 

One-fifth cubic centimetre of the original bouillon culture was injected subcuta- 
neously into a rabbit. On the fourth day temperature 10(3.1o f. Found dead on the 
seventh day with the usual lesions of hog cholera, such as engorged spleen, necrotic 
foci in the liver, reddened Peyer's patches, hemorrhagic points on the lower colon 
and rectum. Spleen and liver contain hog-cholera bacilli in moderate numbers. 
From spleen an agar and a bouillon culture prepared by piercing spleen with a fine 
platinum needle and inoculating culture media tberew.th. In both only hog-cholera 
bacilli appeared. The original spleen culture contained no swine-plague germs, 
otherwise the rabbit would have succumbed withm 1 or 2 days. 

In the gelatine roll appeared after a few days a very large number of the same 

colonies, evidently all hog cholera. ,. i , x • n- 

No 4. October 14. Small male pig, weighing about 30 pounds ; died last night. 

Skin of abdomen slightly reddened. Subcutaneous inguinal glands enlarged, 

cedematous, mottled red and pale. . , , ., ,, ee a c 

Mouth free from ulcers. Content. <.f stomach stained with bile. Mucosa of fundus 

over an area 4 inches square deeply congested, swollen. Slight injection o minute 

vissels in duodenum; remainder of small intestine normal. Large intestine con. 

lains a turbid liquid and a substance resembling coal ashes. The mucosa of cajcnm 

studded with superficial, yellowish sloughs, about the size of pins' heads or a little 

a™! In the colon, besides these small yellowish sloughs there are three or four 

larje areas over which the mucous membraue is entirely necrosed «uperhcuUly^ 

Thfse areas are about 6 inches long. The minute sloughs l.mited chiefly to the 

nnner half of the colon. . , , , . 

iiver ratlier firm in texture, the acini projecting slightly above inter obnlar tissue 
on the surface. Glands near the portal fissure deeply congested throughout. 

Dilatation of pelvis of kidneys encroaching on medullary portion to a large extent. 
Both ureters very much distended; walls from one-half to three-qm.te^-s inch th.ck 

Lungs collapse when removed from thorax; no pleuritis In all the lobes there 
are masses of collapsed and hepatized tissue varying in diameter rom one-half to 
eeverll inches. They are situated chiefly near the roots of the lobes. The smal 
median lobe in part hepatized, bright red with yellowish mottling. In the termina 
bronchi are plugs of lung worms imbedded in thick muco-pus. The tissue around 
the plugs in the left principal lobe hepatized. 

Bacte1-iolo.ical examination: With bits of diseased lung tissue two gelatine rolls 
wet pave^l and a rabbit inoculated. The rolls both contained on the second day 
In mmense number of colonies of micrococci, evidently a contamination of the gela- 
Tne The inoculated rabbit died in 4 days with enlarged sp een and patches of 
necrosis in the liver in the form of a net work. An agar culture from the spleen and 
a bouillon culture from heart's blood both subsequently contained only hog-cho era 
hacTl No swine-plague germs detected, although the rather premature death of 
the rabbit led me to s;spect their presence. Some weeks later a rabbit was inocu- 
lated subcutaneously in the ear with a platinum loop of the blood culture of the 
nrecedin- rabbit. This rabbit died in 5 days with hog-cholera lesions. 
"^ wfh a^bit of spleen pulp of the pig a gelatine roll A and an agar plate B were 
prZared- also aLuillon tube inoculated with platinum needle after pricking the 
Tpleen This developed into a pure culture of hog-cholera bacilli. In the gelatine 
rollTppeared numerous colonies of hog-cholera bacilli. The agar plate was partially 
overgrown ; the few isolated colonies were made up of hog-cholera bacilli. 



36 

From the liver a gelatine roll, au agar aud a bouillon tube inoculated, each -with 
minute particles of tissue. In the roll numerous colonies appeared, evidently all hog 
cholera. The two tube cultures likewise contained only hog-cholera bacilli. 

No. 5. October 15. Small male pig, weighing about 2b i>ouuds, died last night. 

Skin about urinary meatus reddened. Subcutaneous inguinal glands enlarged, 
firm, juicy, faintly mottled with red. 

Stomach contracted. Contents same as in preceding cases. Mucosa in large folds, 
summits of which somewhat reddened. Slight discoloration of muco.sa of lower ileum. 
Contents of large intestine firm, in form of lumps. In the cjecum about ten ulcers, 
from one-eighth to one-half inch in diameter, the largest hutton-shapped, flattisli, a 
firm, yellowish, necrotic base extending into subjacent muscular coat. Complete 
necrosis of Peyer's patch at valve. In the colon a small number of large and small 
button ulcei's. The solitary follicles projecting as large as split peas. When scxueezed 
a white soft mass exudes from a central depression. 

Liver rather firm in text-ure. Gall bladder contains semi-liquid, flaky bile. 

Spleen slightly enlarged. Kidneys on section very pale. 

Both lungs (edematous. Hepatization involves the free tip of both small cephalic 
lobes of the right lung, the major portion of the ventral lobe of the left lung. In 
both principal lobes are a moderate number of small hepatized foci. In both bronchi 
a large quantity of very viscid muco pus, which extends down into the branches of 
the principal lobes. These latter and the terminal portion of the principal bronchi 
contain plugs of luug wortus. Bronchial glands enlarged, firm, pale. 

Bacteriological examination : In cover-glass preparations from the sjileeu a very few 
bacteria resembling somewhat hog-cholera bacilli seen. An agar culture inoculated 
with platinum wire remained sterile. * On the following day spleen taken from re- 
frigerator and a second agar tube inoculated with particle of pulp. In this tube a 
colony of greenish fluorescent bacilli appeared. 

From hepatized lung tissue two gelatine rolls were prepared. The first one was 
spoiled by a few liquefying colonies; the remaining small colonies were inaccessible. 
The second roll remained sterile. 

A rabbit inoculated subeutaneously with a particle of luug tissue died in 24 hours. 
At the place of inoculation considerable purulent thickening of skin with ecchymosis 
of the subcutis. Numerous very small coccidia cysts in liver. Spleen enlarged, 
congested. (Bacteriological notes of this rabbit mislaidr) 

No. 6. October 15. Small female in A^ery poor condition ; died last night ; more or 
less decomposition. Ventral asp'fect of bodj' reddened. Subcutaneous inguinal glands 
enlarged, firm, and Aery hyperiemic. 

Stomach much contracted, empty. Mucosa of fundus beset with punctiform hem- 
orrhages. Small intestine not marked by changes ; one ulcer in lower ileum. Con- 
tents of ca?cum aud colon of a somewhat pasty consistency mixed with coarse sand. 
In the CiT^cum about six old, flattish ulcers, from one-fourth to one-half inch in diam- 
eter, also a iiatch of easily removable, membranous exudate several inches square- 
In the colon near the valve several ulcers and a similar patch of exudate. 

In the lungs the hepatization, though extensive, is more or less scattered in foci as 
follows : 

A few hepatized foci in left cephalic, one large hepatized mass in ventral, and four 
wedge-shaped masses in lef-t principal lobe. In the right lung, fully two-thirds of the 
median and the whole of the veutral lobe solidified. The latter lightly glued to the 
neighboring lobes. Disseminated through it are very many necrotic foci about one- 
eighth inch in diameter. In the right principal lobe several hepatized masses. In 
both bronchi a large number of adult lung worms. Pericardium thickened ; vessels 
injected. Spleen not enlarged or congested. 

Bacteriological examination : Spleen found more or less decomijosed. No germs in 
cover-glass preparation. In an agar culture therefrom numerous isolated and conflu- 
ent hog cholera colonies appeared on following day. 

A rabbit inoculated subeutaneously with a bit of lung tissue (the particular region 



37 

not indicated in the notes) was found (lead ou the eighth day. Extending from tho 
point of inociihitiou over tlie entire ahdonion and portion of tliorax tlie subcutis is 
infiltrated with a yellowish, pasty mass of ])us, stained with blood. The superficial 
layer of ninscles discolored, ecehyiiiotic. Spleen slightly enlarged. No peritonitis. 
Cultures from the spleen remained sterile. An agar plate from the subcutaneous exu- 
date spoiled by condensation water. An agar tube from the same source remained 
sterile. 

No. 7. October 15. Small male pig, of about :]") pounds, died yesterday afternoon 
late and put in refrigerator until next morning. Animal in fairly good condition. 
Tlio lesions in this case were briefly as follows: 

Digestive tract : Fundus of stomach faintly reddened. Small intestine not affected. 
Contents of large intestine liquid, of black color, holding much earth in suspension. 
One nicer on the thickened Peyer's patch near the valve. Follicles swollen. No other 
changes. 

Lungs: General pleuritis indicated on the most dependent portions of the left lun"- 
by a thin, membranous exudate, elsewhere by roughening. The various lobes lightly 
glued together. Hei)atization limited to the tip of tho left ventral and a small area 
in the left principal lobe, containing numerous necrotic foci. In the right principal 
lobe two wedge-shaped, hepatized masses, in which are many minute oval germs, re- 
sembling swiue plague. Generalized bronchitis indicated by much curdy muco-pus 
in the bi'onchi and branches. No lung worms detected. 

In the liver, the center of many lobules in all the lobes of a brick-red color, caused 
by fatty degeneration of this portion of the lobule. Bile very thick, dark-colored. 

Spleen A-ery much enlarged, softened, dark colored. 

Bacteriological examination: From this animal only the spleen and the pleural 
exudate received any attention. An agar tube inoculated from the spleen simply 
with a platinum wire was sterile on the following day, although bacteria had been 
detected in the spleen pulp in cover-glass preparations. A second tube inoculated 
with a particle of pnlj) from the spleen, kept meanwhile in the refrigerator, developed 
a large number of isolated and confluent colonies. So far as could be determiiied 
these were all swine-plague bacteria. No motile bacteria present. 

An agar culture made at the autopsy from the pleural exudate proved to be a pure 
culture of swine-plague bacteria. 

No. 8. October 17. Male pig, weighing about 3.5 pounds, died last night. Sub- 
cutaneous inguinal glands enlarged, ou section dotted with minute petechijc. 

Stomach normal. Duodenum bile-stained. lu lower ileum much liquid, containino- 
flne earth and sand. In ciecum minute vessels of mucosa injected. Peyer's patch at 
valve somewhat swollen and discolored. lu the upper colon several small patches of 
thin exudate, about one-fourth inch in diameter; the .subjacent epithelium appeared 
necrosed. In both kidneys infarcts of a yellowish, homogeneous appearance sur- 
rounded by a hypera?mic zone, and visible from the surface of kidney, two in the left 
and twelve in the right. 

Spleen somewhat enlarged, firm. Liver very pale, pulp rather soft. On tlie left 
lobe several paler spots, not elevated, about one-fourth inch in diameter. Bile thick 
flaky. 

Lungs everywhere adherent to surrounding structures by means of a membranous 
exudate, grayish, elastic, coming away in patches and shreds when pulled. This 
membrane especially thick between lungs and diaphragm. The various lobes matted 
together and adherent to pericardium. Lungs do not collapse. 

Left ventral and cephalic lobes completely hepatized. Throughout both are dis- 
seminated a large number of greenish-white, homogeneous, firm masses from one- 
fourth to one-half inch in diameter. Almost entire right lung hepatized. In the 
cephalic lobe, ventral lobe, and cephalic portion of principal lobe the necrotic masses 
are very numerous, one near tip of ventral lobe quite large. The hepatization of 
the principal lobe is of the dark-red variety. 



38 

Large quantities of lung worms in left bronclius and branches contained in the 
caudal tliird of principal lobe. Right bronchus not opened. Pericardium thickened, 
opaque. Heart surface covered with a thin, transparent pseudo-membrane. Left 
auricle hemorrhagic. A clot distending the right heart and forming of it a complete 
cast. Center of clot pale. 

Bacteriological examination : From spleen two agar cultures made. One remains 
sterile. In the other on second day a faint growth starting from condensation water 
upwards. The latter contains clumps of swme-plague bacteria and large bacilli with 
terminal spore. Several gas bubbles in agar. 

From the pleural exudate of right lung an agar and a bouillon culture prepared at 
autopsy. On following day a large number of punctiform colonies on agar surface. 
Minute flakes in condensation water. In bouillon minute granules, representing 
clumps of minute oval cocci. In both tubes only swine-plague bacteria. 

From the more recently hepatized regions of lungs which contain large numbers of 
swine-plague bacteria and some large bacilli, two gelatine rolls and two agar plates 
prepared. 

In the gelatine roll A two forms of colonies appeared, one with disk homogeneous, 
the other with a distinct peripheral zone. In roll B only one kind a])peared. A 
number of bouillon tubes were inoculated from colonies in roll B which turned out 
to be streptococci. From roll A bits of gelatine were removed to bouillon with 
warmed platinum needle, some cultures remained sterile while others contained 
streptococci. 

On the agar plate A, large numbers of apparently identical colonies appeared. On 
plate B, a moderate number developed. Of these a few examined were made up of 
swine-plague bacteria. 

A large rabbit inoculated with a particle of lung tissue died within 20 hours. No 
internal changes, excepting a probably preexisting fatty condition of the liver. Few 
swine-plague bacteria detected with the microscope. An agar and a bouillon culture 
from heart's blood contained only swijie-plague bacteria on second day. 

No. 9. October 18. Female pig ; died last night ; weighs about 30 jjounds. Sub- 
cutaneous glands of groin enlarged, firm, cortex hyperajmic. 

One small necrotic patch on mucous surface of lower lip. Stomach with fundus 
pale, pyloric region bile-stai ned. Around the cardiac expansion are about thirty 
yellowish-white, confluent, and isolated ulcers from one-eighth to one-fourth inch in 
diameter. They are raised above the level of the mucosa, flat on top. Projecting 
slough soft, friable; base of ulcer very firm, extending into muscular coat. Mucous 
membrane of duodenum bile stained ; arborescent injection of minute vessels. Mucosa 
of ileum more or less discolored and inflamed. Large intestine with walls very much 
infiltrated and mucosa extensively destroyed by necrotic changes. In the caecum, a 
large patch of ulceration having a peculiar gnawed appearance, surrounding islands 
of intact mucosa. On section the mucosa is found converted into a yellowish-white, 
firm mass. 

In the colon patches like these are interspersed with a large number of isolated cir- 
cular ulcers with blackish, depressed surface and a subjacent yellowish, firm, thick 
base extending into the muscular coat. Besides these, there are a considerable num- 
ber of ulcers with an elevated,,soft, necrotic top, easily scraped away. In lower colon, 
large patches of destroyed mucosa. 

Spleen very large, friable, pulp very dark. Liver tissue apparently unaffected. 
Bile rather thick. Kidneys with parenchymatous degeneration of cortex. 

Lungs as whole much affected. In the right lung all but the dorsal third of the 
ventral lobe solid, enlarged, bright red, with large and small masses of a pale-greenish 
color disseminated through it. A portion of the cephalic lobe solid, in the same con- 
dition. One-half of the median lobe similarly diseased. The principal lobe glued to 
ventral lobe by a thin pseudo-membrane. About one-third along the ventral aspect 
solidified in masses from one-half to three-fourths inch in diameter, these masses ex- 
tending from diaphragmatic to convex surface of the lobe. The interlobular tissue 



39 

around these hepatized masses distended with serum. The various lobes of the left 
lung are in the same condition as the corresponding ones of tlie right lung. Pleuritis 
only over the hepatized regions in the form of a delicate network. 

The trachea and bronchi contain much Crotliy muco-pus. In the left terminal 
bronchus, surrounded by hepatized tissue, are masses of lung worms completely occlud- 
ing it. 

Bronohial glands large, palo, containing a variable number of small necrotic foci. 

Bacteriological examination: From the right pleural sac a bouillon and an agar 
tube were inoculated with platinum loop. In both only swine-idague bacteria sub- 
sequently appeared. 

From a more recently hepatized region of the lungs two agar plates were prepared 
■with a loop of the serum, in which microscopic exami.nation had shown an immense 
number of swine-plague bacteria. Plate A contained, after several days, a small num- 
ber of miscellaneous colonies and a very large number of barely visible colonies, which 
proved to be made up of swine-plague bacteria. On Plate B no development. 

From the more advanced disease two gelatine I'olls were prepared from a particle 
of necrotic tissue. Eoll A liquefied. KoU B, after a week's time, contained about 
twenty- live small colonies of the same character, resembling hog cholera, and one large 
colony. The former transferred to agar, and bouillon tubes proved to bo not hog 
cholera but streptococci. 

A rabbit inoculated with a bit of diseased lung tissue died within 20 hours. Organs 
.not changed. At point of inoculation considerable purulent infiltration. In blood 
and spleen a very large number of swine-plague bacteria, showing in stained prepara- 
tions the polar stain very well. Cultures in bouillon and ou agar confirmatory. 

From spleen a particle of pulp used to prepare one bouillon culture and an agar 
plate. In the bouillon the motile hog-cholera bacilli appeared among clumps of 
swine-plague germs. Ou the plate after several days a moderate number of colonies 
of one size and a very large number of colonies of a very small size appeared. Some 
of the former examined are hog-cholera bacilli, the latter swine-plague bacteria. 

From particles of liver tissue the same cultures were made, and the same mixture 
of hog-cholera and swino-plague bacteria found. 

Sections from more recent pneumonic intiJtration prepared from material hardened 
in alcohol show a considerable amount of fibrin in the alveoli, in whose meshes are a 
few leucocytes and very many of the minute swine-plague bacteria. The peribron- 
chial and interlobular lymph spaces are distended with fibrin and cells and contain 
very many swine-plague bacteria. 

Sections prepared from tissue in which the disease is much more advanced show a 
complete occlusion of the alveoli and small air tubes with dense cellular masses in 
■which swine-plague bacteria are more or less abundant. The tissue surrounding such 
foci contains in the alveoli a moderate number of round cells, largely Intermixed 
■with fatty cells. Bacteria absent. 

No. 10. October 19. Small male pig in poor condition, weighing 21 pounds. Died 
last night. Subcutaneous inguinal glands very large. On section punctiform hem- 
orrhages and irregular masses of ai)parently necrosed tissue observed. 

In the stomach a considerable number of single aud confluent ulcers with iiroject- 
ing, yellowish, friable slough, resting on a firm, iodurated, whitish base. The mucosa 
of small intestine shows extensive arborescent injection of minute vessels. 

Contents of large intestine, a chocolate-colored liquid containing much sand. 
The lesions of the mucous membrane are about as extensive as in case 9. The larger 
patches show more diptheritic deposit than in preceding case. 

Spleen very large, blackish, friable. Cystic degeneration of both kidneys. 

Lungs extensively diseased. Nearly the whole of the left lung excepting the caudal 
half of the principal lobe hepatized, and covered with a thick membranous exudate. 
This is readily peeled off in shreds and larger patches, especially dense on the ventral 
and cephalic lobe and adjacent pericardium. Lobes adherent to one another ; adhe- 



40 

Bious easily looBeuetl. The ventral lobe is a raottled bright red. The small air tubes 
occluded with semi-solid plugs, easily squeezed out. This condition not observed in 
the other lobes, excepting in the prin-cipal, in which the terminal bronchus and 
branches are occluded with plugs of lung worms and muco-pus. 

In the right lung, the ventral lobe in the same condition as corresponding lobe of 
left side, containing in addition numerous necrotic foci. The cephalic iifth of prin- 
cipal lobe hepatized ; the hei)atization of a bright red color, with faint regular yel- 
lowish mottling. Cei^halic half of the small median lobe in the same condition. 
The bronchi in the tip of principal lobe occluded with masses of lung worms and in 
part hepatized. In trachea and bronchi much muco-j)us. 

Bacteriological examination : In i)reparations from the spleen bacteria not detected. 
An inclined agar tube inoculated with platinum needle contained in a few days a 
large number of minute apparently identical colonies. So far as could be determined 
no hog-cholera bacteria present. A bouillon culture inocvilated with a particle of 
pulp contained both hog-cholera and swine-plague bacteria. 

From the liver the same cultures prepared. In the agar tube besides a large num- 
ber of small colonies are six larger ones. These consist of hog-cholera bacilli, the 
former of swine-plague bacteria. In the bouillon tube both germs are present. 

No inculations or cultures were made with lung tissue from this case. An agar 
and a bouillon tube were inoculated with a platinum loop from pleural exudate at 
the autopsy. In both only swine-plague germs appeared. 

No. 11. October *22. Black female, weighing 22j^ pounds, died last night. Subcu- 
taneous inguinal glands indurated; cortex reddened. Some hemorrhagic points in 
parenchyma. Fine shreds of exudate on serous surface of large intestine. 

In stomach a small quantity of food. Over the entire fundus the mucosa intensely 
congested and swollen. No ulceration. Small intestine not aftected. Large intes- 
tine contains a small quantity of turbid fluid. Mucosa much pigmented. In the 
caecum and upper colon a small number of ulcers with slightly projecting slough ; 
lower colon considerably congested. Follicles swollen ; when compressed, a white 
curdy plug issues from a central opening. 

Both lungs diseased. In the right lung near the caudal border of principal lobe a 
wedge-shaped mass of hepatized tissue, of a bright red color. The peribronchial 
and interlobular tissue infiltrated over this region, and the pleura covered with a 
thin exudate. In the bronchi of this lobe are masses of mucus and pus in which 
lung worms arc imbedded. In both cei)halic and ventral lobes are masses of hepa- 
tized tissue; in the former also a large necrotic mass. 

The two small lobes of the left lung are converted into a greenish-yellow necrotic 
mass, which cuts like firm cheese. In the principal lobe are three foci of hepatization 
two of them near the tip of the lobe, where the bronchus anabranches are occluded 
with lung worms imbedded in mucus. 

Pericardium thickened, vessels injected. 

Cultures made in bouillon and on agar from pleural exudate. The bouillon culture . 
contained after several days only hog-cholera bacilli. The agar tube was lost. From 
a particle of lung tissue a gelatine roll A, and agar plate B prepared. On the agar 
plate six small colonies appeared, made up of swine-plague bacteria. No colonies ap- 
peared in the gelatine roll. 

A rabbit was inoculated with a particle of lung tissue. It died in 9 days with 
characteristic hog-cholera lesions. Cultures from the spleen contained only hog- 
cholera bacilli. 

From the spleen and liver, bouillon and agar tubes were inoculated with platinum 
wire. In all four tubes only hog-cholera bacilli ax>peared subsequently. 

No. 12. October 26. White female pig, weighing about 30 pounds. Died yesterday 
afternoon and placed in refrigerator until this morning. Subcutaneous inguinal 
glands enlarged, hypersemic. In abdominal cavity some dark-colored serum. 

One ulcer on mucous surface of lower lip and one on gums. Stomach contracted. 



41 

Couftiderable pigmentation of nmcosn. Outside of eanliac ("expansion two ulcers with 
elifjlitly projoetiiif? slough. DuodcMiinu very (U^eply i)igiiieuU;(l. rigiaeutation ex- 
tends through small intestine. Similar dark pigmentation of the mucosa of large in- 
testine. I'eyer's patch at valve converted into nuuuToiis small yellowish sloughs 
with indurated base. A few specimens of trichoceplialus attacluMl to mucosa. In 
upper colon about six small and one larger ulcer with indurated base. Follicles much 
enlarged with purulent contents easily expressed. Mesenteric glands with very 
hypera-mic cortex. 

Both lungs adherent to surrounding structures. In both jdeural sacs a small quan- 
tity of clouded serum. On removing the lungs from thorax, the various lobes are 
found bound together by exudate, the small median lobe Imbedded in it and the 
diaphragm adherent to base of lungs, the intervening exudate being very abundant. 
In the right luug, both ventral and cephalic lobes, hepatized. On section they have 
a red, granular appearance mottled with grayish linos and patches. In the ])rin- 
cipal lobe at its caudal extremity the interlobular tissue distended with reddish 
serum. Luug worms located here in large numbers. The cejihalic portion of this 
lobe where it rests against the ventral lobe is hepatized, bright red and mottled 
with whitish points and patches, differing somewhat from the necrotic foci of former 
descri)itions. 

In the left lung the ventral lobe solid, resembling the corresponding ri<>ht lobe. 
Left principallike the right. Lung worms in the caudal region. 

Pericardium thickened, opaque, distended withyellowish serum. The inner surface 
lined with a partly opaque, partly gelatinousexndate. The heart surface completely 
covered with a thick, spongy pseudo-membrane. (See plate x.) 

Spleen very slightly enlarged and congested. Slight post-mortem changes indi- 
cated m the appearance of the liver. 

Bacteriological examination: In cover-glass preparations from different parts of 
the lung tissue very many swine-plague bacteria detected. Two agar plates and two 
gelatine rolls were prepared. The latter were spoiled. On the second agar plate a 
large number of minute colonies of the same appearance and three or four miscella- 
neous colonies. The small ones are swine-plague bacteria. 

A rabbit inoculated with a particle of lung tissue died within 20 hours. In the 
spleen and blood very many swine-plague germs. In a bouillon culture the peculiar 
growth in minute granules observed which this germ has frequently exhibited here- 
tofore. 

At the autopsy an agar and a bouillon culture were inoculated from each pleural 
sac. In all four tubes only swine-plague bacteria appeared on following dav. 

From spleen and liver, agar and bouillon tubes inoculated, the former with a plati- 
num needle, the latter with a particle of pulp. On the agar surfaces a small number 
of isolated colonies appeared, made up of swine-plague bacteria. In the bouillon 
tubes, besides the clumps of swine-plague bacteria, a large spore-bearing bacillus ap- 
peared in bottom of tubes. 

No. 13. Octo^jer 28. Black female pig weighing 28 pounds. Died last night. Sub- 
cutaneous inguinal glands enlarged, firm, pale red, mottled with gray. 

Mucosa of stomach slightly discolored in fundus, otherwise normal. In duodenum 
mucosa dark bluish iu color, minute vessels injected and occasionally ruptured. 

Contents of large intestine a brownish liquid. Slight pigmentation and injection 
of vessels, no ulceration. 

Liver tissue rather firm to the touch. On the surface of the right half yellowish- 
gray spots, involving from one to several lobules, about one to a square inch. Over 
the entire surface are disseminated minute dots of a red-lead color, each situated iu 
the center of an acinus. Bile thick and flaky. 

Spleen much enlarged, flabby ; pulp dark red. 

In the left lung the dependent half of ventral lobe solid, grayish red, faintly mot- 
tled on the surface. Bronchioles filled with plugs of thick muco-pus. In the central 



42 

portion of the priucipal lobe two small bepatized foci. Numerous lung worms in ter- 
minal bronchus. 

In the right lung between ventral and cephalic lobes a portion of hepatized mot- 
tled lung tissue. Somewhat back of this region a mass of necrotic tissue, separated 
from the surrounding tissue by a greenish-white line and covered by a thick opaqne 
pleura of the same color. In the principal lobe a large wedge-shaped mass of hepa- 
tized tissue extending inwards from the lateral border several inches. On section it 
is dark red, mottled with grayish circles and irregular lines. The pleura much thick- 
ened, opaque. Another wedge-shaped hepatized mass situated near caudal tip, per- 
haps further towards necrosis than the preceding one. Pleura covering it necrosed. 
Lung worms in the terminal bronchus imbedded in mucus. 

Cover-glass preparations from the more recent pneumonic masses show very few 
germs. From the right pleural cavity a bouillon and an agar tube inoculated. In 
the former, motile hog-cholera bacilli; in the latter about seven colonies of the same 
size composed of motile bacilli, probably hog cholera, though they appear somewhat 
too large. A black rabbit inoculated in subcutis with a particle of lung tissue died 
in seven days. At the place of inoculation the subcutis is infiltrated over an area of 
several square inches with pus. No peritonitis; spleen large, containing many hog- 
cholera baciUi; necroses in liver. 

In cover-glass preparations from spleen and liver a considerable number of hog- 
cholera bacilli detected. From spleen an agar and a bouillon tube were inoculated 
with platinum needle. Both contain only hog-cholera bacilli on following day. 
Cultures from the spleen gave the same result. 

The lesions found in these thirteen cases may be summarized briefly 
as follows : 

No. 1. October 12. Extensive hepatization of lungs with necrotic foci; lung 
worms ; exudative pleuritis and pericarditis. Congestion and necrosis of stomach; 
hyperremia, pigmentation, and ulceration of the large intestine; ulcers small, ulcer- 
ation evidently follicular. Only swine-plague bacteria found. 

No. 2. October 12. Spleen large. Fully four-fifths of lungs hepatized, with necro- 
tic foci; pleuritis and pericarditis; lung worms; bronchitis. Small ulcers in large 
intestine. Only swine-plague bacteria found. 

No. 3. October 12. Spleen large. Pneumonia slight ; no pleuritis. Hemorrhagic 
inflammation of stomach. Ulcers in large intestine. Both hog-cholera and swine- 
plague bacteria detected. 

No. 4. October 14. Multiple pneumonic foci in lungs. No pleuritis. Lung worms. 
Hyperajmia of stomach. Ulcers and patches of necrosis in large intestine. Only 
hog-cholera bacilli detected. 

No. 5. October 15. Scattering pneumonic areas ; bronchitis ; lung worms. Ulcers 
in large intestine (button ulcers). Only swine-plague bacteria detected. 

No. 6. October 15. Considerable hepatization of all lobes ; lung worms. Large 
ulcers in large intestine. Only hog-cholera bacilli detected. 

No. 7. October 15. Spleen large. Hepatization not extensive; pleuritis; bron- 
chitis; no lung worms. Only Foyer's patch near valve ulcerated. Only swine-plague 
bacteria found. 

No. 8. October 17. About four-fifths of lung tissue hepatized, with necrotic foci; 
pleuritis and pericarditis. Lung worms. J^o ulcers in large intestine. Infarcts in 
kidneys. Only swine-plague bacteria found. 

No. 9. October 18. About one-half of lung tissue hepatized with necrotic foci; 
pleuritis; lung worms; bronchitis. Necrotic patches and ulcers in stomach and 
large intestine. Spleen large. Both-hog cholera and swine-plague bacteria detected. 

No. 10. October 19. Spleen large. Three-fourths of lung tissue hepatized, with 
necrotic foci; pleuritis; bronchitis; lung worms. Ulceration of stomach and large 



43 

iutestiue as extensive as in No. 9. JSotli .swine-plaguo and bog-cholera bacteria 
present. 

No. 11. October 22. Scatterin"- pncnmonic foci, with extensive necrosis; plearitis; 
pericarditis; lung worms. Congestion of stomach. Small nnraber of ulcers in large 
intestine, pigmentation. Hog-cbolera and swine-plague bacteria present. 

No. 12. October 25. Anterior (cephalic) half of lungs hepatized. Extensive pleur- 
itis and pericarditis; lung worms. Pigmentation of mucosa of large intestine. Few 
nlcers in large intestine ; follicles with purulent contents. Only swine-plague bac- 
teria present. 

No. 13. October 28. Pneumonia not extensive ; pleuritis; bronchitis; lung worms. 
Intestines pigmented; no ulceration. Only hog-cholera bacilli found. 

In all there was pueuraonia more or less extensive, associated in the 
majority of cases with cellular and fibrinous pleuritis, more rarely with 
pericarditis. In the hepatized regions necrotic masses were frequently 
met with. Bronchitis was common ; lung worms were very abundant. 
The lesions of the digestive tract varied from case to case. In some the 
mucosa of the stomach was hypenemic, bordering on hemorrhage ; in 
others diphtheritic and ulcerated ; in still others quite unchanged. The 
lesions of the large intestine ranged from hypersemia and pigmenta- 
tion to the most extensive destruction of the mucous membrane. Of 
the intermediate stages may be mentioned tumefaction of follicles, with 
discharge of purulent contents and subsequent formation of small 
ulcers. 

The results of the bacteriological work may be tabulated as follows : 



No. 



Spleen. 



Liver. 



Lungs. 



Pleura. 



Pericardium. 



Bern arks. 



Swine plague. 

....do 

Hog cholera .. 



Swine plague 



...do 

Stciile 

Tlog cholpia 



Hog cliolfira 



Swine plague 
do 

Swiue plague. 

and hog 

cholera. 
Hog cholera .. 



Swine plague 
do 



Hog cholera 

a n d swiue 

plague. 
Swine plague 

and hog 

cholera. 
Hog cholera . . 



Swine plague. 
Hog cholera.. . 



Hog cholera 

and swine 

plague. 
Swine plague . 

and hog 

cholera. 
Hog cholera . . 



Swine plague. 
Hog cholera . . 



Swine plague 
(?) 



Swino i)laguo 
and strepto- 
co(-c,i. 

Swine plague. 



Swine plague 
and hog 
cholera. 

Swine plague. 

Hog cholera . . 



Swine plague 
do 



Swine plague. 
Sterile 



Swine plague 
..-.do L. 



.do. 



.do. 



Hog cholera 



Swine plague. 
Hog cholera . . 



No hog cholera. 

Do 
Swino plague 

a n il hog 

cholera. 
No swine 

])lague. 
No hog cholera 

No swine 

plague. 
No hog cholera. 
Do. 



Swine plague 
and hog 
cholera. 
Do. 



Do. 



No hog cholera. 
No swine 
plague. 



It will be observed that in six cases (IS^os. 1, 2, 5, 7, 8, and 12) only 
swine-plague bacteria were detected ; in three (Nos. 1, 6, 13) only hog- 
cholera bacteria, and in four (Nos. 3, 9, 10, 11) both were found. In 
general I would not place too much stress on the absence of either kind of 
bacteria, because there is no reason why if both pathogenic species are 



44 

present they should not after a time invade every animal, unless the 
presence of one disease, such as swine plague, would oppose the inva- 
sion of hog cholera in the same animal, a hypothesis for which we have 
no supporting facts. If we turn to the jiositive evidence we find that 
in ten out of thirteen animals the same virulent swine-plague bacteria 
were found. We have, in other words, bacteria pathogenic in pigs, as 
we shall presently show, which travel from animal to animal and pro- 
duce a more or less extensive pneumonia with pleuritis. These facts 
are in themselves sufficient to separate swine plague as a distinct dis- 
ease from hog cholera. 

In those cases thoroughly studied, such as ISTos. 1 and 2, hog-cholera 
bacilli were probably entirely absent. A glance at the table will show 
that when they were detected they were always found in the spleen. 
In ^os. 1 and 2 only swine-plague bacteria were found in the spleen. 
The same may be said of iSTo. 12. Why the hog-cholera bacilli should 
have been in these animals and not appear in any of the numerous cul- 
tures made is certainly incomprehensible. 

Perhaps the best evidence, aside from inoculation, that swine-plague 
bacteria are the cause of tlie pneumonia is deducible from the bacte- 
riological examination of the lungs and pleura. In only two later 
cases were hog-cholera bacilli obtained from the pleura. In one (No. 
13), the lung disease had advanced to caseation, and it accords with 
former experience that in such cases swine-plague bacteria are gone, 
and if hog-cholera bacilli are in the animal they are certain to appear 
in these dead lung masses, and hence in the pleural cavity. In those 
lungs which were extensively hepatized, but in which necrosis had 
not advanced far, the hepatized tissue was practically a pure culture 
of the swine-plague bacteria. The cause of the intestinal lesions must 
remain a matter of doubt, although their nature combined with the 
presence of hog-cholera bacilli in the herd would lead us to regard them 
as due to the latter. 

As to the origin of this mixed outbreak, nothing positive could be 
learned of the former history of the herd. As it was made up of two, 
possibly three lots, it may be assumed that one lot brought one germ 
and another lot the other. This hypothesis gains force from the great 
variation in the extent and character of the lung and intestinal lesions. 
Meanwhile it must be remembered that only one-third of the herd came 
under observation, owing to the rapidity with which the animals suc- 
cumbed and the somewhat tardy information concerning the outbreak 
which reached us. 

THE PRODUCTION OF DISEASE IN SWINE AND OTHER ANIMALS WITH 
THE SWINE-PLA'GUE BACTERIA FROM THIS OUTBREAK. 

The bacteriological notes already given indicate a virulent variety of 
these bacteria, inasmuch as rabbits succumbed to a subcutaneous in- 
oculation of a minute dose within 20 hours. The following tests on 



45 

four pigs were equally striking. The culture used was derived from 
case 2 by inoculatiug a rabbit with a particle of lung tissue. The 
culture from the spleen of this rabbit was again tested about a month 
later on a second rabbit. The agar culture from this animal was used 
to inoculate six agar tubes. From these, when 2 days old, the surface 
growth was washed down into the condensation water with sterile 
bouillon and the turbid liquid transferred to a sterile test tube. With 
this the following inoculatious were made : 

l!^o. 272, 2 cubic centimetres subcutaneously, one-half into each 
thigh. 

No. 273, one-half cubic centimetre into right lung, through chest- 
wall, between fifth and sixth rib. 

No. 274, 1 cubic centimetre into abdomen. 

No. 275, 1^ cubic centimetres into right lung. 

These pigs were all alike, Essex grade, 10 weeks old, and weighed 
about 40 pounds each. The inoculations were made November 16, 5 
p. m. 

No. 272 did not show any ill effects except small tumors at the places of injection 
It was killed December 9 and found normal. 

No. 273 was very sick on the following day. It breathed with difficulty and re- 
fused to rise and eat. On the fourth day there was some improvement. The animal 
began to eat. The improvement continued and on December 2 (16 days after inocu- 
lation) it had apparently fully recovered. On this day it was killed for examination. 

About 100 cubic centimetres pale yellow serum in abdominal cavity. Diaphra"-ui 
pressed downwards and very tense, as viewed from the abdominal side. Lungs ad- 
herent to chest-wall and diaphragm. Both pleural sacs converted into large al)sccss 
cavities, the walls of which are formed by the diaphragm, the chest-wall, and the con- 
vex surface of the lungs. These walls are very much thickened and covered with 
a pulpy yellowish-white layer of pus. The cavity is distended with a turliid, milkv 
fluid. Lungs much compressed, along dorsal border collapsed. Small median lobe 
collapsed. 

Pericardium adherent to heart surface by means of fibrous bands. Pericardial sac 
contains a small quantity pale yellowish turbid li(juid. 

Intestinal tract normal. Liver with many lobules either entirely or only ceutrally 
congested. Serous surface facing diaphragm slightly roughened. 

At this time no swine-plague bacteria were found in the spleen, as the cultures- 
made therefrom with particles of pulp remained sterile. 

No. 274 was found dead early next morning, i. e., within 24 hours after iuociilation. 

The superficial inguinal glands much reddened. The abdomen contains about 100 
cubic centimetres of clouded, straw-colored serum. The serous surface of the 
various abdominal organs exposed by reflection of the abdominal walls covei-ed with 
a thin layer of pale yellowish, friable exudate, thickest on the liver. The exudate 
also found between the coils of intestines. In both pleural sacs from 50 to 75 cubic 
centimetres of turbid serum. Pleuritic exudate on the ventral third of theri^ht 
lung. Similar exudate on the pericai'dium. Lungs normal. Digestive tract normal 
so far as the mucous membrane is concerned. The various lymph glands of thorax 
and abdomen slightly reddened. Liver, spleen, and kidneys not aflected. 

Only the spleen of this case was examined for bacteria. After scorching the sur- 
face an agar and a bouillon culture inoculated with platinum wire. On the agar 
surface about 100 isola'^ed colonies from l^ to 2 millimetres in diameter appeared on 
the following day, all alike and so far as examined made up of swine-plague bacteria. 
The bouillon culture likewise proved to be a pure culture of the injected bacteria. 



46 

No. 275 became very sick after the inoculation. It refueeil to get u]} and eat, and 
breathed with difficulty. It was found dead November 19, i. e., between 2 and 3 
days after the inoculation. 

Skin not discolored. The cut subcutaneous vessels exude drops of dark blood. In 
the abdomen a few elastic threads of coagulated exudate stretched across coils of in- 
testines. 

In right pleural cavity about 100 cubic centimetres of blood-stained serum. Lungs 
adherent to ribs by means of a thick, soft, easily removable exudate. Lobes of right 
lung glued to each other and to pericardium ; they are not enlarged. The pleura of 
the ventral half of principal lobe is converted into a thick, wrinkled, and bleached 
layer; beneath it the lung tissue is hepatized. The dorsal portion of this lobe, still 
air-containing, covered with patches and shreds of exudate. The cephalic and ven- 
tral lobe solidified, not enlarged ; grayish-red on section. 

The left lung likewise covered in part with pleuritic exudate. The ventral two- 
thirds of principal lobe covered with a thick pseudo-membrane and hepatized, very 
firm; on section, red, mottled with gray. The ventral and cephalic lobes collapsed, 
covered with exudate, which extends to contiguous i)ericardium. (See plate vi). 
The entire diaphragmatic portion of pleura of both principal lobes and median lobe 
converted into a wrinkled, necrotic mass. Pericardial sac contains much reddish, 
turbid fluid. The surface of the heart covered with a whitish, firm, roughened exu- 
date. 

Stomach contracted ; contains a small quantity of bile-stained liquid. The mucosa 
of the fundus bluish-red, swollen. The whole covered with a layer of viscid bile- 
stained mucus. The remainder of digestive tract free from iiiilammation. 

In the liver the central region of acini dark brownish red, the outer portion pale 
brownish. 

The presence of the injected swine-plague bacteria in the organs of this animal 
were determined by the following cultures : 

From the spleen, in which no bacteria were detected under the microscope, an agar 
tube inoculated with platinum wire and a bouillon tube by adding a particle of pulp. 
The bouillon tube became clouded with swine plague. The agar tube remained 
sterile. A rabbit inoculated subcutaueously in the ear with a platinum loop dipped 
into the bouillon culture died within 20 hours. In blood and spleen very large num- 
bers of swine-plague bacteria. In cultures from these organs only these germs pres- 
ent. 

A small area on the hepatized left principal lobe scorched, and a small particle cut 
out with flamed scissors. From the serum filling the cavity thus formed, which con- 
tained large numbers of swiue-i)lague bacteria, one gelatine roll, and from this two 
agar jjlates prepared. The roll remained free from growth ; also one agar plate. 
On the other appeared a large number of minute colonies and several large colonies 
of hacillus suhtilis. The former were identified as swine-plague colonies. From the 
left pleural exudate an agar tube was inoculated. Abundant growth of swine-i)lague 
bacteria on the following day. 

From the hepatized region of the left princii)al lobe portions were placed in alco- 
hol and subsequently sections prepared. The alveoli and small air tubes densely 
packed with masses of cellular exudate. The interlobular tissue distended with a 
network of fibrin and a scanty number of leucocytes. In the contiguous, still per- 
vious areas, some air tubes were occluded with cellular plugs, and either around these 
or independent of them Avere isolated groups of alveoli occluded with round cells. 
Swine-plague bacteria were present in enormous numbers both in the parenchyma 
and the interlobular tissue. They were densely and uniformly sprinkled around and 
between the cells, in some places forming dense zooglcea. They were much smaller 
than in cultures, being just visible at 500 diameters. (See plate xi, figs. 2 and 3.) 

These iuoculatious show that these bacteria injected subcutaneously 
have little or no effect, but when introduced into one of the large se- 



47 

rous cavities severe iiiflammatiou is aroused followed by si)eedy death, 
lu No. 275, the injection into the right lung led to a typical pleuro-pneu- 
nionia of the left lung, such as was encouutered iu tlie outbreak from 
which the bacteria were isolated. 

These bacteria were fatal to mice aud guinea-pigs and to pigeons iu 
large doses : 

December 13. — Two mice inoculated under skin of back with a loop of growth from 
an agar culture one day old. Both dead next moruiug, with spleen much swollen 
and containing large numbers of the inoculated bacteria. From the spleen of one an 
agar aud a bouillon culture were made. The bouillon became faintly clouded ; on 
the agar numerous conllueut colonies appeared. Only swine-plague bacteria detected 
in these cultures. 

From the same culture a guinea-pig was inoculated subcutaneously in the same 
way. The guinea-pig lived 12 days. No lesions except a fatty condition of liver 
found at autopsy. A tube of agar to which 2 drops of blood were added remained 
sterile. 

At the same time two fowls and two pigeons were inoculated, one fowl and one 
pigeon with a loop of the agar culture subcutaneously and one fowl and one pigeon 
with 1 cubic centimetre of a peptone bouillon culture one day old. The needle of 
the syringe penetrated the superficial muscular layer of one pectoral muscle. 

Both fowls remained well, also the pigeon inoculated with the loop. The other 
pigeon dead next day. On the right pectoral region the subcutis was infiltrated and 
of a reddish-yellow color, the subjacent muscular tissue discolored to a depth of one- 
fourth to one-half inch. Lungs congested, other organs normal. In the blood num- 
erous swine-plague bacteria giving the polar stain ; in the liver very few. 

In April, 1891, about H years after these bacteria had been obtained from this out- 
break, the following inoculations were made to determine how much of their viru- 
lence had been lost by cultivation. 

Jiriil 13. — With a loop rubbed over an agar culture 4 days old, a large gray rabbit 
was inoculated by inserting the looi) into an incision on the ear made with flamed 
lancet. Rabbit dead next morning. In blood and spleen swine-plague bacteria iu 
moderate abundance. 

Jjrril 21. — Two guinea-pigs weighing IJ pounds each received a subcutaneous injec- 
tion of 0.075 and 0.15 cubic centimetres of a turbid suspension of swine-plague 
bacteria from an agar culture 1 day old. 

The guinea-pig which had received the largest dose died in 2G hours. At the place 
of injection slight yellowish infiltration of subcutis. No peritonitis. In both pleu- 
ral sacs a large quantity of a grayish, partly gelatinous efiusion, contaiuing immense 
numbers of bacteria. Pericardial sac similarly involved. Both lungs dark bluish 
red throughout; tissue still floats. 

The other gwinea-pig very sick for several days, recovered, and was killed on the 
eighth day. At the place of injection a minute ulcerous opening from which pus 
could be pressed. In the subcutis considerable rather firm infiltration, surrounded 
by patches of blood extravasation. Internal organs not afiected. 

YIII. 

In November, 1889, an outbreak of swine plague came to the notice 
of the Bureau, which, in some respects, has a quite remarkable history. 
The information given below was obtained by Dr. Kilborne. 

An educational institution near this city was in the habit of keeping 
on its inclosure a small number of swine in pens which were arranged 



48 

m the mauuer iudicated in the figure. The slope of the ground was 
from yard 1 to yard 3, and from yard 5 to yard 3. 



Yd. 2. 


Yd, 3. 


Yard h 


P£N. 2. 


Pen. 3. 


Yd.4. 


Peh.1. 




Pen. 4. 






Pen. 5. 


Yd. 5. 



In September a boar, 5 months old, died in pen 1. There had been 
no disease on the place 2 years previous to this occurrence, and no recent 
jjurchase of pigs. In the latter part of October ten pigs, 2 months old, 
were purchased, five placed in pen 1, and five in pen 5. At this time a 
sow in pen 2 had four pigs, all of which died in a few days, while the 
sow, although sick for a time, recovered. 

In pen 3 a sow became sick very suddenly November 8, and died next 
day. A litter of seven pigs, 7 weeks old and small f ^^ their age, died 
within 4 days after the death of the sow. Of these, five came underour 
observation (jSTos. 1 to 5 inclusive, of the autopsy notes). These five, 
after a very careful examination, proved to be cases of swine plague. 
While the recently purchased pigs in pen 1 remained unaffected, those 
in pen 5 began to die at the same time that the young pigs in pen 3 
were dying. Thus two died November 9 and one November 10. One 
of these was carefully examined, and to our surprise the disease was 
found to be hog cholera, as the autopsy notes (No. C) clearly show. 
The remainder were taken to the Experiment Station. At the same 
time there were in pen 4 two pigs about 5 months old and one old sow. 
One of the pigs, sick November 12, was transferred to the Experiment 
Station, where it w^as found dead on the following morning. This case 
also was one of hog cholera (Case 7). By feeding the viscera of these 
two pigs to fresh pigs an outbreak of hog cholera was produced, which 
was subsequently utilized in a series of experiments on vaccination, as a 
means of exposing swine which had been vaccinated beforehand. 

On inquiry over a mouth later, we were informed that no further 
losses from swine diseases had been sustained. 

In the following pages are given the notes of the autopsies and 
bacteriological examination of the litter of small pigs which died in pen 
3. They are all the more interesting in that the diseasei was swine, 



49 

l)lague imcomplicated with hog cholera. The autopsy uotes of the two 
hog-cholera cases from peu 5 and i)eii 4 are appended, to complete the 
history of this remarkable outbreak. 

2s^ovemb6r 11, lbb9.— Pig No. 1, wliite Icinalo, weighs abuut 15 poitiuLs. Died last 
night. Cousideiable reddening of the skin over the ventral aspect of the body. 

Stomach contains a small quantity of a yellowish viscid liquid. Fundus covered 
with mucus and intensely reddened and swollen. In the large intestine, mucosa 
slightly discolored ; in a few places somewhat reddened. No necrosis or ulceration. 
Glands of the meso-colou enlarged, indurated, pale. 

About one-half of both lungs hepatized, the disease limited to the ventral or de- 
l)endent half. The various lol)es adherent to one auotlier, to pericardium and dia- 
phragm by means of a thin, papery pseudo-membrane, which is removable. Tlie hepa- 
tization is very firm ; on section, grayisli red or red mottled with gray. Near the roots 
of the lobes, also on diaphragnjatic surface of the lungs, are considerable numbers of 
small necrotic masses, surrounded by a bluish zone. In the trachea and bronchi, red- 
dish froth ; in the distal extremities of both bronchi, lungworms imbedded in mucus. 

Spleen small, not congested. Liver exceedingly firm to the touch. Surface not 
smooth, owing to acini slightly projecting above interlobular tissue. 

Bacteriological examination : Preparations from hepatized lung tissue contain an 
immense number of very minute oval bacteria. Those from the pleural exudate con- 
tain a smaller number. On one of the inincipal lobes the pleura w-as scorched over 
the diseased portion, and with a particle of tissue from Avithin the scorched area, a 
gelatine roll A, and two agar plates B, prepared. In the gelatine roll appeared, after 
a few days, a large number of barely visible colonies. A week later, besides these, a 
smaller number of colonies, 4 to .^> times larger than the preceding, had appeared. 
Owing to the large number of colonies microscopic examination not successful. 
Minute bits of gelatine were removed at different intervals with warmed i>latinum 
wire and transferred to peptone bouillon. In these tubes only swine-plague germs 
appeared. The larger colonies may have been streptococci, as they failed to develop in 
the bouillon. Both agar plates, after several days, contained a largo number of iden- 
tical quite small colonies, which were found to be swino plague colonies by micro- 
scopic examination and transfer to bouillon. In order to determine whether any other 
bacteria were present, two bouillon tubes Avere inoculated directly from the lungs, by 
piercing them with a i)latinum wire and transferring this to the bouillon. In both 
tubes only sivine-plague bacteria appeared. 

A rabbit inoculated at the same time with a particle of lung tissue died in "> days. 
The subcutaneous tissue over abdomen extensively thickened by a i)urulent and gel- 
atinous infiltrate extending over part of thorax. The abdominal walls are thickened 
and glued to the viscera. These latter covered with a rather firm elastic exudate, which 
dips down between the coils. The serosa is sprinkled with pnnctiform ecchymoses. 
Sjileen small ; thoracic organs not affected. In the abdominal exudate are immense 
numbers of oval bacteria, staining rather feebly. These not detected in spleen and 
blood. An agar tube inoculated from the spleen contained but a single swine-iilague 
colony. A gelatine culture from the blood shows in the track of the needle about 
12 minute round colonies. In a bouillon culture from the peritoneal exudate only 
swine-plague bacteria developed. 

From the pleural exudate of the pig an agar and a bouillon tube inoculated at the 
autopsy. In the former a considerable number of isolated and continent colonies of 
swine-plague bacteria appeared. Tlie bouillon cultuie likewise contains only swine- 
plague bacteria. 

From the spleen jiulp, in which no bacteria were detected, a particle placed in an 
agar and a bouillon tube. Both were sterile on the following day. On the third day 
faint cloudiness of the bouillon, which contained only swine-plague germs. In the 
agar tube the condensation waterwasclouded, and a grayish membrane starting from 
it ascending along agar surface. Only swine-plague bacteria detected in this growth. 
1614 4 



50 

Portions of Inng tissue from different lobes, hardened in alcohol, were examined. 
Sections from recently affected lung tissue, bordering on normal tissue, showed the 
alveoli to be filled in some lobules with blood corpuscles and fibrin ; in others there 
was, in addition, a filling up of scattered alveoli with round cells. In still others the 
alveolar capillaries were greatly distended with corpuscles, almost occluding the al- 
veoli. Imbedded in the fibrinous plugs of the alveoli were colonies of minute cocci, 
almost every alveolus containing one or more such colonies. lu sections from tissues 
iu more advanced stages there were, in addition to the more dense cell infiltration, 
large masses of the minute bacteria occupying the alveoli in some iiortious of the 
section, Auy regularity in the distribution of these bacteria not observed. 

No. 2. Examined at the same time. White female, weight 15 pounds. Skin on 
ventral aspect of body moderately reddened. Subcutaneous inguinal glands hy- 
pera-mic. 

Stomach contains a small quantity of turbid liquid. Mucosa of fundus consider- 
ably reddened. In the small intestine the vessels of villi appear injected, especially 
in duodenum. In the caecum au.d colon the entire mucosa has an intense purplish hue, 
shading into a wine color. This most marked in the caecum and upper 4 or 5 inches 
of colon, where the epithelium appears necrosed. The inflammation gradually dimin- 
ishes and disappears iu the rectum. 

Exudative pleuritis as in case 1 ; the psendo membrane as thick as heavy paper. 
About two-thirds of right lung hepatized. The cephalic and ventral lobe entirely 
solidified, also adjoining half ofthe principal lobe. In the caudal portion of the latter 
several hepatized foci. Lung worms in terminal bronchus. The tip of cephalic lobe 
completely necrosed. The ventral lobe contains large, yellowish-white, homogeneous 
foci of dead tissue. Median lobe completely hepatized. Through it are disseminated 
necrotic foci. 

In left lung, principal lobe entirely hepatized. Hemorrhagic, grayish-red, and 
grayish lobules found on the same cut surface. Ventral and cephalic lobes merely 
congested. Pericardium thickened. 

Spleen small, pulp darker than normal and softened. Liver as in No. 1. Bile very 
thick, dark-colored. 

Bacteriological examination : An agar and a bouillon tube were inoculated each 
with a particle of spleen pulp. The agar tube remained sterile. The bouillon be- 
came faintly clouded on the second day and contained only swine-plague bacteria. 

The hepatized lung tissue and pleural exudate both show presence of swine plague 
germs; the lung tissue contains immense numbers of them. With a bit ofthe latter 
a gelatine roll A and agar plate B prepared. In the gelatine roll, a considerable 
number of very minute brownish colonies appeared within a week. They were all 
alike. Several transferred to bouillon at intervals and the resulting cultures care- 
fully examined. Only swine-i)lagne bacteria detected. The agar plate had a moder- 
ate number of colonies, those growing on surface from 2 to 3 millimetres in diameter. 
These also proved to be swine plague when examined and transferred to bouillon for 
further identification. 

At the autopsy an agar and a bouillon tube were inoculated from the right pleural 
cavity. On the agar appeared a large number of isolated and confluent colonies all 
apparently alike. Some of these, as well as the growth in the condensation water, 
were examined and found to be swine-plagne bacteria. The bouillon contained also 
a streptococcus and a bacillus, imparting a sour smell to the culture. A rabbit in- 
oculated with a particle of lung tissue died in 6 days. The subcutaneous infiltra- 
tion and the peritonitis precisely as in the rabbit inoculated from No. 1. The spleen 
contained scarcely any, the blood few, and the peritoneal exudate an immense number 
of swine-plague bacteria. Agar cultures from exudate and blood and a bouillon cul- 
ture from the exudate contained only swine-plague bacteria. 

The presence of swine-plague bacteria on the inflamed mucosa of cajcum was dem- 
onstrated by inoculating a rabbit with a particle of mucosa which had been washed 



51 

in sterile water. Eabbit died in 2 days with considerable local infiltration, but no 
peritonitis. An agar culture from spleen with platinum needle remained sterile. A 
bouillon culture from blood became clouded with swine-plague bacteria. To further 
test this germ, one-eighth cubic centimetre of this bouillon culture 7 days old was 
injected subcutaneously into a rabbit. It lived 11 days. Tbore was extensive i>uru- 
lent infiltration of the subcutis over abdomen and thorax. Internal organs normal. 
But one (bouillon) tube inoculated with particle of liver tissue. This reiuaiued clear. 

No. 3 exauiiued on same day. White female weighing 18 pounds. Died last night. 

Ventral aspect of body considerably reddened. Stomach as in preceding cases. 
Mucosa of duodenum very much reddened ; the remainder of the small intestine nor- 
mal. Mucosa of caecum and colon not quite so intensely inllamed as in No. 2. Indi- 
cations of a yellowish, soft exudate appearing in small masses as part of the feces. 
Its microscopic characters not determined. 

Double exudative pleuritis, the exudate, thick on diaphragm which firmly adheres 
to lungs, very slight on convex surface of lungs where it appears as a roughening or 
a very delicate membrane. The various lobes glued to each other and to pericardium. 

In the left lung the two smaller lobes (ventral and cephalic) in a condition of pale- 
red hepatization ; very slightly enlarged. lu the principal lobe four or five foci of 
dark-red hepatization imbedded in normal tissue, on section marked with grayish, 
irregular lines. These masses are elevated slightly above the surrounding tissue and 
covered with a thick, opaque, greenish-white pleura. In the right lung both smaller 
lobes hepatized, larger than the corresponding left lobes, very lirni to the touch. The 
cut surface sprinkled with minute grayish masses. In the principal lobe the hepa- 
tized masses are dark red in color. The small median lobe enveloped in exudate and 
hepatized, the cut surface grayish red. 

In the bronchi a small quantity of reddish, frothy liquid. In the right terminal 
bronchus lung worms. Bronchial glands very large, firm, yellowish white. 

Pericardium inflamed, opaque. In left heart a firm washed, clot imbedded in a 
dark, soft coagulum. The right heart distended with a dark, soft coagulum. 

Spleen small, dark-colored. Liver and bile as in No. 2. 

Bacteriological examination: From the spleen an agar and a bouillon tube inoc- 
ulated with a particle of pulp. After several days a grayish growth, spreading from 
bit of spleen, composed of rather large cocci. The bouillon tube at this time also 
clouded ; contains only swine-plague germs. 

Two similar cultures prepared from the liver. In the bouillon tube only swine- 
plague bacteria appeared. On the agar surface three colonies present, one of these 
a chromogene, the others large spore-bearing bacilli. In the turbid condensation 
water the same large bacilli and swine-plague bacteria intermingled. In cover-glass 
preparations from spleen and liver no germs could be detected. 

From the right pleural cavity an agar and a bouillon tube inoculated. IJotli re- 
mained sterile. 

From the most recently hepatized lung tissue, which contains large numbers of 
swine-plague bacteria, a gelatine roll A and an agar plate B prepared. In thegeliitine 
roll colonies appeared answering to the description given for those under case 1. 

The bouillon tubes prepared from the colonies contained no hog-cholera germs at 
anytime. Swine-plague bacteria and possilily streptococci were present, although 
this is somewhat doubtful. The agar jdate B remained free from growth. A bouil- 
lon tube inocculated with a platinum needle thrust into the hepatized lung remained 
sterile. 

A rabbit inoculated with a particle of lung tissue succumbed to the disease in H 
days, with extensive subcutaneous purulent infiltration over abdomen. No peritoni- 
tis. Cover-glass prej)aration8 and cnltures from blood and spleen are negative. 

From this lung sections were cut from portions of one principal lobe hardened in 
alcohol. The alveoli were nearly all occluded by round cells, among which in a cer- 
tain number of alveoli large masses of the very minute swine-plague bacteria could 



52 

be detected. The small air tubes likewise filled with densely packed cell masses. The 
interlobular tissue iu a state of inflammatory oedema. 

November 12. — No. 4, small female, weighing about twenty pounds. Died last 
night. Veutral surface of the body moderately reddeued. Considerable quantity of 
subcutaneous fat. Lymphatic glands in groin slightly enlarged and reddened. 

Oue ulcer at base of left lower front tooth. Stomach contracted aud contains a 
email quantity of liquid resembling tomato juice. The mucosa of fundus over an area 
3 inches in diameter of a dark wine-red color ; the hypertemia extends through entire 
mucous layer. Ou the surface a very delicate, easily removable pseudo-m'/ubraue. 
Mucosa of duodenum pigmented and bile-stained. In lower ileum some patches of 
punctiform ecchymosis. In large intestine feces adhering rather firmly to mucosa, 
which is reddeued and pigmented in spots aud patches aud somewhat rough to the 
touch. 

In thracic cavity lungs covered with false membrane and in part adherentto chest- 
wall and pericardium. On removing them, the pleuritis and hepatization found 
nearly as extensive as in the preceding case, i. e., the greater part of both small lobes 
in each lung hepatized and exceedingly firm ; in the principal lobes disseminated foci 
of hepatization both of the grayish-rod aud the hemorrhagic type. Lung worms not 
detected. In the air tubes of the ventral lobes cylinders of whitish pus. In the large 
bronchi reddish frothy liquid. Pericarditis as iu preceding case. On the epicardium 
a very delicate pseudo-membrane. 

Liver tissue very firm to the touch ; bile thick. Pyramidal portion of kidneys dark 
red. Spleen small, somewhat darker colored thau in normal condition. 

Bacteriological examination : Cover-glass preparations of the pleural exudate show 
a moderate number of swine-plague bacteria. In the lung tissue there are immense 
numbers of these bacteria, with au occasional large bacillus amongst them. From the 
right pleural cavity au agar and a bouillon tube, from the left an agar tube inoculated 
at the autopsy. In these tubes a considerable number of identical colonies appeared 
made uji of swine-plague bacteria. In the coudensatiou water of au agar culture 
from right pleura occasional streptococci to be seen. The bouillon tube became uni- 
formly clouded with swine-plague bacteria. After two weeks a few very large colo- 
nies of strange bacteria had developed in both agar tubes. 

With a particle of lung tissue a gelatine roll A and an agar plate B prepared. Koll 
A broke ; plate B showed in a few days about 50 colonies, evidently alike. Those 
examined and transferred to bouillon consisted only of swine-plague bacteria. 

A rabbit inoculated with a particle of lung tissue remained imaftected. Another 
rabbit received a subcutaneous injection of one-eighth cubic centimetre bouillon from 
au agar colony of lung plate. This rabbit died in 13 days with a very large abscess 
at the point of inoculation. 

In the spleen of i)ig no bacteria were detected with the microscope. In the liver 
several germs resembling swine-plague bacteria were observed. With particles of 
liver aud spleen tissue two agar and two bouillon tubes were inoculated. Only the 
bouillon tube from the liver became fertile and contained a diplococcus; no swine- 
plague bacteria. 

Sections from the lung tissue hardened in alcohol aud stained in various ways weie 
carefully examined. In the same section were lobules in which the alveoli contained 
fibrin and very few cells, others iu which much desquamation of the epithelial cells 
had taken place, and others in which the alveoli were occluded by dense cell masses. 
In some places the septa had apparently disappeared and a coutiuuous plug of densely 
massed cells extended through a number of continuous alveoli. The small air-tubes 
were likewise filled up with cell masses. The interlobular tissue distended with 
serum, the lymph channels similarly distended and containing masses of leucocytes. 
Iu all alveoli excepting those containing only the desquamated cells, the very minute 
oval swine-plague bacteria are present in immense numbers, disseminated singly 
through the (Edematous tissue and in large zoogloea amongst the cellular masses. 



53 

Xovemher l.i. — No. 5, .sinall white male, weiji;lit about 10 pounds. Died last night. 

In the digestive tract ot this case uothiug abnormal excepting a sonu'what bluish 
coloration of the mucosa of large intestine and swelling of the solitary follicles, the 
contents of which cau be expressed through a central opening. 

About one-third of the entire lung tissue hepatized. The disease involves the ven- 
tral tliird of all the lobes, excepting the left cephalic, Avhich is free from pneumonia. 
The median lobe completely solidified and containing two necrotic foci. A thick 
pseudo-membrane covers the pleura of the diseased areas. In the bronchi and 
branches of the principal lobes numerous plugs of lung worms imbedded in mucus. 
The bronchi of the ventral lobes occluded by cylindrical masses of mucus and pus. 

Bacteriological examination : An agar tube inoculated from the right pleural cav- 
ity at the autopsy- contained subsequently 5 colonies of swine-plague bacteria. 

Cover-glass preparations of diseased lung tissue show large numbers of pus corpus- 
cles, amongst these small oval bacteria, probably swine plague, and occasional chains 
of streptococci. A gelatine roll culture A and an agar plate B were made from par- 
ticles of lung tissue. In roll A there appeared, after a week, about onehuiulred colo- 
nies of bacillufi coli, twelve colonies of a slowly liquefying chromogeno,and a very large 
number of colonies just showing a disk under the microscope. Particles of gelatine 
containing these minute colonies were removed to bouillon, but no development took 
place. On the ag.ar plate about ten colonies of swine-plague bacteria appeared, which 
grew quite large, owing to isolated position. Transferred to a bouUion their swine 
plague nature confirmed. 

With a particle of lung tissue a large black rabbit inoculated. Dead in five days. 
The subcutis was extensively infiltrated and thickened as in previous cases. Peri- 
tonitis absent. Spleen barely enlarged. In cover-glass preparations from spleen and 
liver no bacteria observed. In an agar culture from blood thirty swine-plague colo- 
nies appeared. After a week a fleshy, whitish growth composed of large motile bacilli 
starts from condensation water upwards on agar surface. In an agar culture from 
the liver-a considerable number of swine-plague colonies appeared. In a bouillon 
culture from spleen only swine-plague bacteria developed. 

With particles of spleen pulp of the pig an agar and a bouillon tube inoculated. The 
bouillon became very turbid, greenish, fluorescent and contained a small motile bacil- 
lus. Plate cultures from this proved the bacillus a liquefying fluorescent bacillus. 
In the agar tube a growth started from jiarticle of spleen down the inclined surface 
and subse<iuently imparted to the agar a greenish tint. The same bacillus as that 
found in the bouillon culture present. No swine plague bacteria detected. 

In all five pigs specimens of trichocephalus were attached to mucosa of ca'cum and 
upper colon. 

The following tables give a brief summary of the facts obtained: 

Pig Xo. 1. November 11, one-half of lungs hepatized ; some necrotic 
foci. Exudative pleuritis, pericarditis. Lung worms. Catarrhal inflam- 
mation of stomach. Only swine plague bacteria present. 

Pig No. 2. November 11, two-thirds of lungs hepatized; many necrotic 
foci. Pleuritis, pericarditis. Lung worms. Ilyperaimia of stomach. 
Intense hyperaunia of large intestine. 

Pig No. 3. November 11, one-half of lungs hepatized ; pleuritis: peri- 
carditis; lung worms; hyi)era!mia of stomach and large intestine. 

Pig No. 4. November 12, one-half of lungs hepatized ; i)leuritis and 
pericarditis ; bronchitis ; hyperemia of stomach, of large intestine 
slight. 

Pig No. 5. November 13, one-third of lungs hepatized; pleuritis; 



54 

bronchitis; lung worms; swelling of solitary follicles of large intes- 
tine, contents expressible. 



Pig 

No. 


Lunga. 


Pleura. 


Spleen. 


Liver. 


Intestines. 


1 
2 
3 

4 

5 


Swine plague 

.-do 

.do 


Swine plague 


Swine plague . 




Swine plague. 






...do 


Swine plague - 
Negative 

...do 


.do 


Swine plague and 

streptococci. 
Swine plague 


Negative 

...do 


Swineplague, bac. 
coli, clitouiogene. 







It will be observed that these five animals died of swine plague pure 
and simple. Hog-cholera bacilli were absent. An examination of the 
pathological notes shows in every case extensive pneumonia, accom- 
panied by exudative pleuritis and terminating in some cases in necrosis 
of lung tissue. Perhaps the most instructive feature of the disease 
is the inflammation of the stomach and large intestine, which was 
especially marked in the second case. In the third, besides the intense 
hypersemia, there was evidence of exudation. 

That such intense hyperiemia, provided the bacteria continue to act 
on the membrane, or provided they are of the proper degree of viru- 
lence, may lead to croupous and diphtheritic deposits and subsequent 
ulceration, needs no comment. Moreover, the swelling of the solitary 
follicles with discharge of contents, as observed in No. 5, may lead to 
subsequent ulceration. It is interesting to note that the disease reached 
its severest expression in No. 2, both as regards lungs and intestines, 
and in later cases the lesions became less extensive. 

The table giving the results of the bacteriological work shows a grad- 
ual disappearance of the swine-plague bacteria and the invasion of other 
bacteria. Thus, in the spleens of Nos. 1, 2, and 3, swine-plague bacteria 
were detected while the cultures from the spleens of Nos. 4 and 5 re- 
mained sterile. That these bacteria perish very speedily in the body 
is highly probable when we bear in mind that they die very rapidly in 
culture media, a fact to be pointed out further on. 

The swine-plague bacteria causing this outbreak were not so virulent 
as those of the preceding one as demonstrated by the inoculation of 
rabbits from lung tissue and pure cultures. While those of the pre- 
ceding outbreak destroyed rabbits in 20 hours, these were fatal in from 
2 to 13 days, according to the size and age of the rabbit. The following 
inoculation, made about 4 weeks after the last case was examined, serves 
as an additional illustration : 

December 6, 1869. — A large white rabbit inoculated subcutaneously on right ear 
with a loop rubbed over the growth of an agar culture. The animal was found dead 
December 10. From the place of inoculation on the right ear, suppuration had ex- 
tended down over the muscles of the neck. In right jileural sac, on pleura of ribs 
and right Inug, a thick creamy deposit. A similar, more consistent exudate on epi- 
cardium, which is more or less ecchymosed. Other organs not affected. 



55 

After constant cultivation of tliis germ for a year and a half on agar, 
it had lost its virulence to a large extent, so that subcutaneous iuocu- 
latiou produced merely a local abscess. While small doses injected iuto 
the circulation failed to kill a rabbit larger doses were still rapidly fatal. 

March 3i, 1891. — A rabbit receives nudcr the skiu of abdomen 0.2 cubic ceutiuietre 
of a bouillon culture prepared from an agar culture one day old. The rabbit sub- 
sequently seemed sligbtly ill, but recovered. It was cblorofernied on tbe tbirtecutb 
day. Over au area several incbes square tbe subcutis is tbickeued by purulent in- 
liltration, and tbe skin gangrenous and very dry and bard. Tbe abdominal muscles 
sligbtly eccbymosed. Internal organs not affected. 

April 13. — Large wbite rabbit receives into ear vein 0.3 cubic centimetre of a bouil- 
lon culture 24 bours old. Tbe rabbit sbowed signs of sligbt illness for a time. It 
began to grow tbin, and after several weeks it was noticed to move witb great diffi- 
culty. Cbloroformed on tbe nincteentb day. Very aua.niic and tbin. Internal 
organs pale but normal, excepting kidneys, of wbich cortex is fatty. Several ab- 
scesses under tbe fascia of tbe left knee joint, containing a bluisb milky pus. Gland 
in rigbt axilla converted into au abscess. 

Ajyril 29. — From an agar culture 4 days old a turbid suspension of tbe condensation 
water was injected into an ear vein of two rabbits; one received one-fourtb cubic 
centimetre, the otlier one-balf cubic centimetre. 

Botb very quiet and drowsy on the following day; breathing accelerated; one 
with head drawn backward. 

May 1. — Both dead this morning. In tbe first animal tbe bead partially drawn 
backwards on neck. Spleen dark, large, and softened. No peritonitis. Liver very 
pale; on left lobes much interlobular pale yellowish mottling. Cloudy swelling of 
cortex of kidneys. Fatty degeneration of heart muscle. Right btart distended 
with dark, partly coagulated blood ; in left, a small quantity. Both lungs u'dema- 
tous ; right hypostatic. In spleen and blood a moderate number of bacteria showing 
polar stain very clearly. Cultures from spleen and blood contain only the injected 
bacteria. 

In the second rabbit same position of head. Peritonitis indicated by a viscid exu- 
date on ciECum and stretching between coils of intestine when these are separated. 
On liver and spleen a pseudo-membrane. The exudate consists of endothelium in 
state of fatty degeneration, strands of fibrin, leucocytes and large numbers of bac- 
teria showing polar stain. Spleen, liver, kidneys, and blood contain no bacteria 
visible in cover-glass preparations. Liver and kidneys hyperajmic. Heart in dias- 
tole. Both sides contain dark, partly coagulated blood] heart muscle fatty. 
Lungs, especially ventral portions, congested. Cultures the same as in preceding 
case. 

While there existed the difference in pathogenic power between the 
bacteria of this and the preceding outbreak, none could be detected 
from a biological and morphological standpoint. 

The question naturally arises, why should such attenuated bacteria 
as these produce such a severe disease ? The age of the infected ani- 
mals probably will answer this question. Observers have not infre- 
quently noted the fact that bacteria sufficiently attenuated to be harm- 
less to old animals prove fatal to the young. The Pasteur school has 
made use of this observation in increasing the virulence of pathogenic 
bacteria by first passing them through young animals. It is claimed 
that after a number of inoculations these bacteria become fatal to older 
animals as well. 



56 

Having thus demonstrated an outbreak of pure swine plague among 
the animals in pen 3, let us turn briefly to the diseased swine in the 
other pens which came under observation. It will be remembered that 
one pig from pen 5 died November 10, and was taken to the Experiment 
Station, where it was kept in the refrigerator until ISTovember 11. The 
subject is sufficiently important to warrant the reproduction of the notes : 

No. 6. Stomacli contracted ; contains a small quantity of food. One nicer at the mar- 
gin of tbe oesophageal expansion, the latter covered with a thin brownish-yellow layer 
of desquamated epithelium. In the ileum small ulcers, about 2 to a square inch, one- 
eighth inch across ; adherent slough stained yellow. Extensive ulceration in caecum 
and upper colon. The ulcers vary from one-eighth to one-half inch in diameter, black- 
ish on the surface. The base cousists of a firm yellowish-white tissue extendiug into 
muscular coat. Six inches below the valve one large, button-shaped ulcer, the firm 
base extending to serosa and three-eighth inch think. The serosa under it discolored 
and the meso-colou adherent to it. In the lower colon are a large number of circular 
pale spots on the discolored, pigmented mucosa, representing probably the places to 
which exudates had been attached but now shed. 

Lymph glands in lesser omentum and meso-caecum with cortex hemorrhagic. 

In left pleural cavity large patches of blood extravasation under pleura of ribs. 
No pleuritis. Posterior mediastinal and bronchial glands hemorrhagic. Throughout 
the entire hing tissue are disseminated hepatized foci of various sizes surrounded by 
healthy and more or less emphysematous tissue. Thus in the right lung about one- 
half of both cephalic and ventral lobes aud a small volume of principal lobe involved. 
In the left lung one-half of cephalic lobe and tip of ventral lobe hepatized ; in the 
principal lobe six small foci. One-half of median lobe hepatized. The small air 
tubes plugged with thick muco-pus. In the principal lobe several of the foci directly 
traceable to plugs of lung worms, which are very abundant. 

Spleen somewhat enlarged, discolored ; pulp soft. 

Bacteriological examination: In spleen pulp a considerable number of bog-cholera 
bacteria detected. An agar and a bouillon tube inoculated with platinum wire. In 
the former a considerable number of isolated colonies of the same size appear, which 
are, so far as examined, hog-cholera bacilli. In the bouillon tube only hog-cholera 
bacilli observed. A rabbit inoculated with a particle of spleen pulp died in 4 days. 
At the point of inoculation a small abscess. Spleen large, dark, softened ; contains a 
a few hog-cholera bacilli. Numerous very small points of necrosis on liver surfaces. 
In an agar culture from the spleen only hog-cholera bacilli detected. 

With a p.article of lung tissue in which a few hog-cholera bacilli were observed a 
gelatine roll A and an agar plate B prepared. In the roll there were present at end 
of a week a large number of small brownish colonies and about fifty several times 
larger. By carefully removing the smaller ones to bouillon these were found to be 
hog-cholera bacilli. The large colonies not examined. On the agar plate a consider- 
able number of vigorous hog-cholera colonies appeared in 2 days. 

Case 7. November 13. Large white female, .5 months old, weight 6.5 pounds. Ven- 
tral aspect of body and ears bluish red. Subcutaneous fat abundant. Lymj)hatic 
glands of groin with surface imrplish aud parenchyma mottled red and graj'. A 
small number of ecchymoses on abdominal side of diaphragm. Spleen very large, 
blackish, soft. 

Stomach partly filled with food. Mucosa of fundus, and, in fact, of fully one-third 
the whole area of stomach surface, intensely reddened. The hyperjemia extends to 
submucous tissue. Slight ecchymosis and pigmentation of duodenum. Occasional 
petechiaa iu ileum; Peyer's patch near valve pigmented. Entire mucosa of cnscum 
and colon purplish gray aud dotted with petechi;e. On mucosa of caicum about 30 
pale circular spots slightly dejiressed, which evidently were the seat of adherent 
sloughs or exudates. In rectum petechiai ; glands of meso-colon hemorrhagic. 



57 

lu the principal lobo of left liiug a bright red hepatizftl mass about three- quarters 
of an inch in diameter; in the right corresponding lobe a mass half as large. In 
the bronchi of these lobes very many lung worms and a considerable quantity of red- 
dish gelatinous mucus. No other hepatization and no plouritis observed. On the 
surface of the lungs a few petechia'. The location of the hepatizations makes it 
probable that lung worms were the original cause. 

Liver shows marked post-mortem changes. Kidneys with cortical portion dotted 
with numerous hemorrhagic points. Clots of blood surrounding papillro. 

In the spleen were observed hog cholera and large bacilli. In an agar culture with 
wire numeruos hog cholera colonies appeared. 

It is a remarkable fact that there shoukl be two diseases of difierent 
nature in adjoining pens at abont the same time. It is not improbable 
that hog cholera was brought with the ten pigs, but in this case it is 
quite curious that those in pen 1 were not attacked. We must as- 
sume that perhaps but one pig was chronically infected (old ulcers) and 
that this pig i)laced in pen 5 formed the starting point of a slowly de- 
veloping infection among the others. 

IX. 

In July, IS.OO, the attention of the Bureau was called to an outbreak of 
swine disease of a very fatal character about 2 miles northwest of Pleas- 
antville, New Jersey. Veterinarian F. L. Kilborne visited this locality 
July 21 and obtained the following information from Mr. Joseph Young, 
the owner of the diseased herd, who gave us all the facilities in his 
command for the investigation of this plague. 

On May 0, 1890, Mr. Young bought forty-five pigs, 2i to 3 months ohl, 
collected by a dealer from several counties. May 23, a second herd of 
fifty-two pigs was obtained from the same source. In this lot were 
noticed several unthrifty animals, and coughing was heard up to the 
time of the appearance of the disease. About July 1 they began to die, 
one of the unthrifty ones being the first to succumb. Deaths, at first 
few in number, increased until the number reached from three to eight 
per day. Thus from July 1 to July 19 thirty-four perished. Ou July 
20 four died, on July 21 seven died, on July 22 eight died. 

No swine had been on this farm for several years except four animals, 
which had been raised and fattened last seasou and which had always 
been in good health. 

The herd was watered from a well, the waste being permitted to 
run into a little depression or wallow in a dry sandy soil. The food 
cousisted of slops, brought over from Atlantic Citj^ in boats. Several 
other herds in the neighborhood were being fed in the same way with- 
out any untoward results at the time. It should be stated, however, 
that later several other herds in the neighborhood became infected. 
This information did not reach us until after the disease had died out. 

The symptoms noted by the observant owner were coughing, loss of 
appetite, and occasional vomiting. The animals strayed into bushes 
and other hiding places, soon became lean and gaunt and weak in the 



58 

hind quarters. They died 3 to 5 days after showing signs of disease. 
Some lived longer, others died quite suddenly. 

Of the forty-two pigs remaining July 23, twenty died between July 
23 and July 28, five died on the Experiment Station, and only seven, out 
of a total of ninety-seven, lived through the disease. 

Seventeen animals came under our observation. Of these, twelve 
were examined on the farm and the remaining five sent alive by express 
to the Experiment Station. Here they all died within a week after their 
arrival. Of those examined on the farm, JSTos. 1 to 4, inclusive, and 
Nos. 11 and 12, came under Dr. Kilborne's observation. From Nos. 5 
to 10, inclusive, cultures were made on the farm by the writer. Cul- 
tures were therefore made from eleven cases only. 

The bacteriological examination of Nos. 5 to 10, inclusive, can not be 
regarded as thorough, owiug to the innumerable insect pests on the 
farm. Much work, however, was bestowed upon Nos. 13 to 17, inclu- 
sive, which died at the Station. The notes of this outbreak are reported 
in detail, while the usual summary will be given farther on. 

No. 1. July 21, 1890. Weight of auimal about 50 pounds. Skiu uot reddened. A 
few delicate fibrils of exudate stretching over coils of intestines. Spleen very much 
enlarged, congested. 

Digestive tract. Stomach contains a small quantity of food. Mucosa of fundus 
intensely hypertemic, bordering on hemorrhage. 

Small intestine nearly normal. Contents of large intestine liquid. The mucosa 
of ciecum and entire colon nearly concealed by a layer of dirty, greenish-yellow, diph- 
theritic membrane, quite readily scraped away, exposing a deeply reddened, raw 
surface. 

Right lung normal. The entire left lung is covered with a pale yellowish (friable) 
exudate, which glues this lung to surrounding parts. The lung itself contains 
masses of hepatized tissue, aggregating, perhaps, one-fourth of the entire lung. 

The lymphatic glands generally are enlarged ; the cortex, and sometimes medul- 
lary portion also, infiltrated with blood. Other viscera not markedly changed. 

No. 2. July 21, 1890. Weight of animal about 75 pounds. Died very suddenly 
during the day. No skiu lesions. Spleen barely larger than normal. 

Digestive tract. Only the large intestine was markedly affected. The mucosa 
extensively pigmented with occasional patches of hyperemia. In colon just below 
the valve one nicer one-half inch across and a few smaller ones discovered. 

Each pleural sac contained nearly 500 cubic centimetres of slightly-clouded serum 
containing large masses of gelatinous coagula. The lungs free from pneumonia. 

Lymphatic glands and remaining viscera not diseased. 

No. 3. July 22. Weighs about 40 pounds ; died during the night. Had been sick 
at least a week according to statement of owner. Spleen moderately gorged with 
blood. 

Digestive tract. The mucosa of caecum and upper half of colon more or less pig- 
mented and beset with rather deep ulcers from one-eighth to one-third inch in 
diameter. 

Fully three-fourths of the right lung is hepatized and contains a few necrotic 
caseous masses. The pleura of this lung covered with considerable pale yellowish 
exudate and adherent to pericardium. Left lung and pleura normal. 

No. 4. July 22. Animal died quite unexpectedly last night. Slight exudative 
peritonitis. Spleen engorged. 

Digestive tract. Stomach normal, filled with food. Mucosa of large intestine 
extensively pigmented, merging into hypersemia in the lower colon. Numerous 



59 

elevated button-like ulcers one-fourth to tliice-fouitbs inch in diameter, extending 
from cu'cum to lower colon. 

In both lungs a small number of pneumonic foci, apparently of an acute character. 
Slight quantity of pleuritic exudate in the right pleural sac. 

Lymphatic glands in general with cortex engorged with blood. Petechia' in the 
cortex of kidneys, beneath peritoneal covering of diaphragm, stomach, and walls of 
abdomen. 

No. 5. July 22. Pig died between 10 a. ni. and 6 p. m.; examined at 7 p. m. Super- 
licial lymphatic glands of the groin hyporamiic throughout; cortex has a purplish 
color. In the digestive tract the mucosa of the fundus of the stomach involved in 
hemorrhagic intlammation with superficial necrosis. In the ca5cum and upper colon 
the mucosa is superficially necrosed. 

In both pleural sacs a considerable amount of pale yellow serum. The interlobu- 
lar tissue of the lungs distended with it. No hepatization. Fatty degeneration of 
the cortex of kidneys. 

This was the first animal from which cultures were attempted. A tube of gela- 
tine was inoculated with a bit of spleen tissue. Subsequently liquefaction took place. 
The turbid liqnefied mass covered by a viscid pellicle. The small bacillus causing 
this liquefaction grew in the same manner in bouillon. It formed a viscid surface 
membrane very speedily, leaving the liquid clear. 

An agar tube which was inoculaied with a bit of spleen tissue remained sterile. 
Similarly two agar tubes inoculated with a loop of serum from both pleural cavities 
failed to develop. A pipette of pleural eifusion collected at the autopsy and sealed 
was examined subsequently at the laboratory. It contained a large spore-bearing 
bacillus and some short rods in chains. In order to detect the presence of auy swine- 
plague germs in the serum, a bouillon culture was also made from the serum, in which 
of course the several germs developed together. A rabbit inoculated in the ear with 
a drop of this culture remained well. Neither swine-plague nor hog-cholera bacteria 
were thus obtained from this animal. 

No. G. Pig killed in what appears to be a dying condition. No lesions found in 
lungs or digestive tract. Spleen somewhat enlarged but firm, not congested. 

From the spleen of this animal a minute bit was i)laced in tube of gelatine and 
of agar. Both remained permanently free from growth. 

From the liver two similar cultures were made. In the gelatine tube a fungus had 
developed after a week, but no bacteria. In the agar tube large spore-bearing bacilli 
appeared in the condensation water. 

Neither swine-plague nor hog-cholera bacilli were obtained from this case. 

No. 7. White pig, died in course of the day. Examined with Nos. 5 and G. Ecchymoses 
on adductor muscles of the thigh. Hemorrhagic condition of cortex of lymphatic 
glands. Petechia' under serosa of small and large intestines. Hemorrhagic inflamma- 
tion of serous covering of ureters and bladder. Cortex of kidneys enlarged, pale, fatty. 
Lungs and digestive tract not afi^ected. 

A bit of spleen placed in a tube of gelatine and a tube of agar failed to give rise 
to any growth in these tubes subsequently. 

In an agar tube inoculated with a bit of liver tissue, a large spore-bearing bacillus 
was found which grew only in the condensation water and not on the surface. 

No. 8. Pig killed in a dying condition. Affected with umbilical hernia. The 
mucosa of the large intestine was deeply pigmented, both lungs extensively hepa- 
tized. Spleen moderately enlarged A gelatine and an agar tube inoculated with 
bits of si)leen tissue, both negative. 

No. 9. Died in course of the day ; examined between 7 and 8 p. m. Spleen large, 
gorged with blood. Pneumonia in localized regions throughout both lungs. Lung- 
worms present. The mucosa of the large intestine of a dark bluish color with scat- 
tering whitish spots of slight exudation. From this case only an agar tube was 
inoculated with a i)article of spleen tissue. On July 24, two days later, there had 



60 

appeared on the inclined surface of the agar about thirty isolated colonies, circular, 
slightly convex, 1^ millimetres iu diameter, grayish, translucent. The clear conden- 
sation water contained a flocculent deposit. Colonies and condensation water show 
minnte oval cocci apparently identical with swine-plague bacteria. 

From these colonies a peptone bouillon tube, an agar tube, and a gelatine tube were 
inoculated August 25. On the following day the liquid culture contained minute 
clumps adheriug to sides of tube. Liquid nearly clear. The agar tube showed a 
delicate grayish line on the surface. Both tubes contained only the minute oval 
cocci. The gelatine tube remained /ree/rom growth. To test the pathogenic nature 
of the germ a rabbit was inoculated in the ear from a colony of the original spleen 
culture July 28. (This sabbit had been inoculated Jane 3 into the thigh with a 
very attenuated culture of swine-plague bacteria sent to the laboratory.) The rab- 
bit died in 2^ days. From the original inoculation an abscess as large as a hen's egg 
had formed on the superficial muscular layer of the thigh. Spleen much enlarged, 
soft. In stained cover-glass preparations of spleen, liver, aud blood numerous swine- 
plague bacteria were detected. A tube of agar was inoculated from the blood and a 
tube of bouillon from the spleen. On the following day a uniform grayish glistening 
layer had appeared on the agar surface, made up, so far as the microscopic exami- 
nation could go, of non-motile oval cocci. The bouillon culture, uniformly clouded, 
contained the same bacteria only. These were readily identified as swine-plague bac- 
teria. 

No. 10. This animal died during the night; examined at 7 a. ra. next morning, 
July 23. Subcutaneous lymphaiic glands in the groin very large, in part henior 
rhagic. Spleen enlarged, firm, not congested. In the digestive tract the mucosa of 
cjecum is concealed by a very thin necrotic layer; mucosa itself purplish. This con- 
gestion extends along entire colon ; meso-colic lymphatics hemorrhagic. 

In thorax, the base of all lobes of both lungs involved in bright red hepatization. 
Pleural sacs contain considerable serum which distends also the interlobular tissue. 
Heart muscle quite pale and discolored in patches. 

A small number of tube cultures in agar and gelatine were prepared at the autopsy 
as follows : 

An agar tube inoculated with a bit of spleen tissue showed no growth on the fol- 
lowing day. Condensation water turbid, however, containing a large spore-bearing 
bacillus, the bacillus becoming spindle-shaped or nearly spherical when the spore 
fully matured. No other bacteria detected. On the second day a faint growth had 
extended on the agar surface, and a small motile bacillus detected. Agar plates weire 
then made to isolate this bacillus, which was quite easily accomplished since the large 
spore-bearing bacillus failed to grow on plates. The small bacillus formed grayish, 
slightly gelatinous surface colonies. It was actively motile, the motion being chiefly 
a twirl with little change of place. Careful subsequent tests showed it to be entirely 
diflerent from the hog-cholera bacillus with which it might have been confounded. 

From the kidney two minute bits of tissue were transferred, one to a tube of agar, 
the other to gelatine. The agar tube contained on the following day about fifty col- 
onies of the same germ found iu the spleen culture of No. 9, i. e., swine plague. In 
the condensation water the large spore-bearing bacillus was also present, and a few 
gas bubbles in the agar. The gelatine tube showed very slight liquefaction of the 
gelatine on the surface where the bit of kiduey tissue lay. This was probably due 
to the large bacillus which did not develop any more in this situation. 

From the liver an agar and a gelatine tube culture were ijrepared in the same 
manner. 

In the agar tube a considerable number of colonies of the swine-plague bacteria 
had appeared July 25. No other germs subsequently detected. In the gelatine cul- 
ture slight liquefaction took place, owing to the presence of an actively motile bacillus 
in chains. 

An agar tube inoculated from the pleural effusion remained sterile. 



61 

With the swiuc-plaguo biicteria from the liver a rabbit was inoculated in the ear 
by pricking the skin with lancet ami inserting a platinum wire dipped into a colony 
on agar. Kabbit dead next morning. Inoculation wound on oar bluish and all veins 
distended. Similarly veins of sul)cutis filled with blood. Spleen enlarged, con- 
gested. Liver in large part invaded by coccidia. In the blood and spleen nuuiorous 
bacteria detected showing the polar stain. An agar and a bouillon culture from the 
blood and spleen contain subseciueutly only the same germs found in tJie tissues. 
Bouillon faintly clouded, no clumps present. Agar growth like that from case 9. 

Sections from the lung tissue of case 10 hardened in alcohol were stained in alka- 
line methylene blue and alum carmine. The interlobular tissue was greatly distended, 
containing a network of fibrin and very few cells. The alveoli contained a slight 
amount of fibrin and very few cells. Throughout the specimens were individual fila- 
ments and bundles of filaments of a rather large bacillus, evidently the same as that 
obtained in one culture. Occasionally in the contents of the alveoli were seen scat- 
tered bacteria of the size and form of swine-plague bacteria. 

Sections from a subcutaneous inguinal gland hardened in alcohol and stained in 
alkaline methylene blue revealed large areas infiltrated with blood corpuscles and 
penetrated by distended blood vessels. In addition to the large bacilli found in the 
lung tissue clumps of very small oval bacteria, identical in apprarance with swine- 
plague bacteria, were found scattered over the entire section, the clumps being largest 
in the hemorrhagic area. 

In sections from the spleen none but the largo bacilli were detected. The spleen 
was extensively loaded with blood pigment. 

The two following cases were examined by Dr. Kilborue on the farm on the morn- 
ing of July 28. Both had succumbed during the night. No bacteriological examina- 
tion was made, but the notes are given to show the extreme variation in the lesions 
of this outbreak. 

No. 11. Subcutaueous inguinal glands very large, hemorrhagic on section. Spleen 
very large, dark, friable. Mucosa of fundus of stomach very hyper;emic. Numerous 
petechiie in mucosa of small intestine. Mucosa of large intestine intensely con- 
gested, portions almost hemorrhagic ; depressed ulcers on Peyer's patch near valve, 
covered with a thin slough ; one is over one-half inch in diameter. In the upper colon 
are large branny patches of superficial necrosis, besides numerous smaller, round 
points of necrosis. The various abdominal lymph glands with very hyperajuiic 
cortex. 

In thorax both pleural sacs contain 100 cubic centimetres of clouded serum. The 
costal and pulmonary pleura covered with a yellowish, friable, membranous exudate, 
causing mutual adhesion of the various lobes. Pericardial sac not invaded. The 
major portion of both lungs hepatized, only the principal lobes being in i)art still 
pervious. Hepatized lobes dark red. Bronchial glands hemorrhagic. 

No. 12. Peritonitis indicated by the presence of 100 to 150 cubic centimetres of 
serous exudate in abdominal cavity. Some few fibrils of coagulated lymph stretched 
over intestines ; extensive serous eftusiou between layers of meso-colon. Spleen 
aftected like that of No. 11, though less markedly so. 

Stomach contains about a litre of food ; mucosa pale and covered with abundant 
tenacious mucus. Slight ecchymosis of upper duodenum. In lower duodenum and 
some feet in length of jejunum the walls infiltrated with extra vasated blood to twice 
the normal thickness. Mucosa of a deep red color and partly covered by patches of 
friable yellowish exudate readily removable. Considerable blood in lower small 
intestine with slight ecchymosis of mucosa. 

Mucosa of large intestine more or less pigmented. In ciecum are three ulcers one- 
fourth to one-half inch in diameter, the subjacent tissue being thickened by intiltra- 
tion from one-half to three-fourths inch. On Peyer's patch near valve, and in upper 
and middle colon, are about half a dozen similar large depressed ulcers with very 
thick base, and some smaller ones. 



62 

In the lungs the cephalic and ventral lobes are involved in pale red hepatization 
■without pleurisy. 

The abdominal and thoracic lymph glands more or less hemorrhagic throughout 
their substance. 

The following five sick animals were sent by express to the Experi- 
ment Station of the Bureau July 28. They reached the Station next 
day and were placed in a disinfected pen. 

No. 13 dies July 31, 3 p. m. ; placed in refrigerator until August 1. Weighs about 
30 pounds. Skin on ventral aspect of body more or less reddened ; over the ster- 
num a few excoriations. The enlarged inguinal glands show as lumps under the skin. 
On section they present a mottled gray and red surface, the red limited chiefly to 
the cortex, ffidema of the subcutis over right knee. 

False membrane covers the left half of the mass of intestines and the spleen ; con- 
sists of an elastic, rather firm yellowish white layer. Spleen tirmly glued to the 
surrounding intestines, slightly enlarged, dark, softened. Liver firm, cuts with con- 
siderable difficulty. Kidneys in condition of parenchymatous degeneration. One 
hemorrhagic spot in medullary portion of one kidney. Pelvis contains a whitish 
glairy liquid. 

Digestive tract. Two superficial necroses on the inner surface of lower lip in front, 
one on the upper lip and on edge of tongue near tip. Stomach contains a little 
deeply bile-stained lluid. Mucosa sprinkled with red spots of a washed-out appear- 
ance, most numerous in fundus and near pyloric valve. Hypera'uiia of duodenum 
begins sharply at pyloric valve. From the opening of bile duct a few drops of thick 
bile can be expressed. Remainder of small intestine not markedly changed. The 
Peyer's patch in lower ileum has some of its follicles enlarged from which caseous 
masses can be expressed. 

Large intestine contains much sand and gravel. Mucosa of ca'cum of a dark slate 
color. The summit of the folds of a purplish hue. Free edge of valve bordered by a 
thin slough. On Peyer's patch near valve areas of necrotic tissue of a yellowish color, 
resting on a iirm, yellowish-white base three-sixteenths of an inch thick. Upper 
colon has its mucosa of the same dark slate color, merging into a wine red. Two 
Tilcers one-eighth of an inch in diameter observed. In lower colon congestion slight 
and gradually disappearing towards rectum. A small number of circular whitish 
erosions, apparently associated with the solitary follicles. 

Thorax. Of the left lung, the ventral and cephalic lobes are interspersed with 
small regions of collapse. The remainder of the lobes very emphysematous and hy- 
peraMuic. Of the right lung, the anterior half (t. e., including cephalic, ventral, and 
adjacent portion of principal lobe) hepatized, covered by a thin false membrane, 
gluing the various lobes lightly to each other and to chest wall. The diseased lobes 
show the regular mottling in the upper, dorsal portion. As we proceed towards the 
ventral portion the mottling is less distinct, the tissue firmer and interspersed with 
small, irregular, necrotic foci. The smaller bronchi contain a thick, whitish pus. In 
ventral lobe a portion of the parenchyma as large as a marble completely converted 
iuto a grayish-yellow homogeneous mass. Of the principal lobe about one-third or 
one-fourth hepatized. The mottling of surface very regular. On section grayish, 
circumscribed areas one-half inch iu diameter interspersed. Over these masses the 
pleura is converted into a wrinkled, roughened, hide-like membrane. 

Trachea and bronchi contain small quantities of foamy liquid intermingled with 
yellowish particles. Bronchial glands barely enlarged, firm; some lobules pale, 
others reddened. 

Bacteriological notes. At the autopsy an agar tube was inoculated with a j)latinum 
loop lightly rubbed over the pleural exudate. Ou following day a thin grayish 
growth with condensation water clouded. Examination of hanging drop and stained 
coverglass preparations shows only swine-plague germs. 



63 

In cover- glass preparations of hepatized Inng tissue a large number of germs re- 
sembling swine-plagiic bacteria ^ere seen, also some other iorms. Two agar plates 
were made from the lung by thoroughly scorching the pleural surface, cutting out of 
the scorched area a bit of tissue and transferring with platinum loop the scrum collect- 
ing in this minute cavity to 10 cubic centimetres sterilized water. With one loop of 
water 10 cubic centimetres agar was inoculated for Plate A. From this agar two 
loops were transferred to agar for Plate B. On following day about five colonies ap- 
peared on Plate A. These were made up of various bacteria. Plate B remained 
sterile. At the same time a bouillon culture was made from the lung tissue. In it 
several germs grew. These were plated. No swine-plague germs obtained. 

With a bit of hepatized lung tissue, obtained as described above, a rabbit was in- 
oculated subcutaneously August 12, 2 p. m. The rabb't was dead next morning at 
8 a. m.,-i. e., in less than 18 hours. In spleen, liver, and blood preparations numerous 
polar-stained swine-plague germs present. An agar culture from heart's blood con- 
tained only swine-plague germs. 

From the peritoneal exudate of pig, consisting of cells and fibrin and numerous 
bacteria of several varieties, two agar plate cultures were made. On Plate A one 
large colony of spore-bearing bacilli and one small colony of swine-plague germs. 
Plate B completely overgrown by the spore-bearing bacillus. 

A bouillon culture from the exudate contains streptococci and swine-plague bacte- 
ria. Agar plate cultures were made therefrom and both germs isolated. 

At the same time a large rabbit was inoculated subcutaneously with a bit of the 
exudate. Dead within 18 hours. Stained cover-glass preparations of blood from 
heart, spleen, and liver tissue show polar-stained swine-plague germs. An agar cul- 
ture from the blood contains only swiue-plague germs. 

From the spleen, after thoroughly scorching through the exudate, two agar plate 
cultures and a bouillon culture were made with bits of spleen pulp. The bouillon 
culture contained only swiue-plague germs. On Plate A several hundred colonies 
appeared next day. The superficial ones from 2 to 3 millimetres in diameter with cir- 
cular, sharply outlined, slightly convex disk of a grayish glistening appearance. 
Those examined were made up of swine-plague germs. Plate B remained free from 
growth. 

The swine-plague bacteria were thus obtained from lungs, pleura, spleen, and peri- 
toneal exudate, while hog-cholera bacilli, which were looked for with the greatest 
care, could not be found. 

No. 14. Died late August 3, and was kept in refrigerator until next morning. Be- 
fore death frequent, liquid, yellowish discharges were observed. 

On the left side, extending from sternum to the left forelinib, the subcufis over the 
pectoral muscle is infiltrated with a gelatinous blood-stained serum. The right pec- 
toral muscle somewhat discolored by extension of the process. A discolored, blood- 
stained area in the abdominal muscle on the left side. 

Considerable post-mortem changes, in spite of the fact that the animal was kept 
on ice over night. Spleen very large, dark, soft: the tissue surrounding it stained 
.with coloring matter of the blood. 

Mucosa of stomach in fundus very hypertemic, partly hemorrhagic. The cardiac 
expansion covered with a thin, blackish, removable layer. In the large intestine the 
lymphoid patch near valve is partly necrosed. About 6 inches below valve a firm 
neoplastic button, about 1 inch in diameter and one-fourth inch thick. In ca'cum 
and parts of colon are numerous small (one-eighth inch) superficial necroses. Mucosa 
injected. 

Lungs considerably diseased. Of the right lung the ventral, adjacent portion of 
principal, and small median lobe are hepatized. On the left side both cephalic 
and ventral are solidified. These diseased lobes are several times larger than the 
normal collapsed lung, very firm and nodular to the touch. They are covered by 
shreds and patches of exudate, gluing the lobes firmly to each other, to the pericardium 
and diaphragm. The nodular condition is due to the presence of a large number of 



64 

firm, yellowish, caseous masses, varying from oue-fourtli to three-fourths inch in 
diameter, dispersed through the hepatized tissue. 

Bacteriological exaniinatiou included the spleen, the lungs, and the pleural cavity. 
At the autopsy an agar tube was inoculated with a bit of pleural exudate. Small 
colonies appeared on the agar surface on the following day, some made up of what 
appeared to be strejitococci, others of micrococci. From this a bouillon culture was 
prepared, and the latter plated on the following day. From these paltes a coccus, 
growing in clumps and short chains, and a large bacillus, were isolated. At the same 
time a rabbit was iuoculated in the ear from the agar culture. The rabbit died in 11 
days. At the point of inoculation was a large ulcer. Spleen small. Cultures from 
various organs on agar and in bouillon remained sterile. 

With a bit of hepatized lung tissue a rabbit was inoculated in the ear. Dead in 8 
days. Ulcer at the point of inoculation. Right lung hepatized. Pleural cavity con- 
tains some blood-stained serum. Cultures from this animal likewise remain sterile. 

From a bit of lung tissue agar plates were also made. On plate A ouly two colo- 
nies appeared made up of large micrococci ; on plate B a thin grayish growth made 
up of spore-bearing bacilli. 

From the spleen two agar plates were made, from which a large coccus and hacillus 
Uiiorescens were isolated. A bouillon culture made directly from the spleen was 
also plated with the result of finding a streptococcus and a large micrococcus. 

No. 15. Male i)ig, weight about 35 pounds. Died yesterday and at once placed in 
refrigerator until morning. 

On abdomen and inner aspect of thighs a few reddish scabs. Spleen somewhat en- 
larged and congested. 

Digestive tract : One ulcer on tip of tongue. Stomach contains a small quantity of 
muddy liquid. Cardiac expansion of cesophagus covered by a yellowish, easily re- 
movable layer of friable material. The mucosa dotted with small red pits. In fundus 
adeeply reddened area of small extent covered with a thin necrotic layer. Duodenum, 
commencing with pyloric valve, of a slate color and deeply pigmented in spots. Pig- 
mentation and aboresceut iujection extends down the small intestine. In large in- 
testiue considerable pigmentation of mucosa. In caecum and upper 12 inches of colon 
are a large number of extensive ulcers of irregular outliue, varying in length from 
one-half to several inches. They are slightly depressed and covered by ochre-yellow 
sloughs scraped away with difficulty. The entire depth of mucosa necrosed. Ileo- 
cajcal valve completely encircled by a band of necrosis. Below the first 12 inches of 
colon the necrosed areas are slightly raised above the surface. No marked thicken- 
ing or infiltration beneath them. In addition to the larger iJatches there are small, 
slightly depressed, round ulcers one-eighth to three -sixteenths inch in diameter, with 
adherent superficial slough. 

Of the lung tissue, a portion of the right ventral, an adjacent portion of principal 
lobe, and part of left ventral lobe collapsed, of a red flesh color ; no pneumonic infiltra- 
tion perceptible. In the bronchi aud extending into branches are small quantities 
of translucent, very gelatinous mucus. In the collapsed right ventral lobe the small 
air tubes contain whitish cylindrical plugs of mucus and pus. 

Urine very turbid, contains much calcic oxalate but no albumen. Bacteriological 
examination w^as limited to the lungs, spleen, liver, and kidneys. 

From the collapsed lung tissue agar-plate cultures were made with a minute bit of 
tissue. Plate A on following day contained numerous isolated and oue sj) reading 
colony; the latter made up of motile spore-bearing bacilli, the former of swine- 
plague bacteria. Plate B showed but two grayish flat colonies, composed of large 
cocci. 

A rabbit inoculated subcutaneously with a bit of lung tissue was found dead on 
the morning of the second day. At the point of inoculation more or less extravasa- 
tion of blood. About 25 cubic centimetres of blood-stained serum in abdominal cav- 
ity. Liver has a red clay color. Cultures on agar and bouillon from heart's blood 
and spleen contain only swine-plague bacteria. 



65 

Cover-fflass pr()i)aratiousof si)loen pulp from pi<;- sliowcd some large (post-mortem) 
bacilli. Oil an agar i)late both swiue-plaguo bacteria ami motile, bacilli resembling 
hog cholera were isc>lated. These motile bacilli were carefully studied and compared 
with hog-cholera bacilli. The results are given farther on.* 

From the liver, iii which a fetv large bacilli were observed in cover-glass prepara- 
tions, a bouillon and an agar culture were prepared. In both there appeared swine- 
plague bacteria and streptococci. Tliese were isolatc<l on agar plates. A rabbit in- 
occulated from the bouillon culture by a prick in the ear was dead in less than 20 
hours. On small intestine nnmerous ecchymoses. Si)leen somewhat enlarged ; lungs 
hypersomic. From blood and spleen cultures were made and cover-glass preparations 
examined. All showed swine-plague germs and these only. 

From the kidney, which apparently contained no bacteria, an agar and a bouillon 
culture were made with minute bits of tissue. The latter remained sterile. The 
former showed Haky masses of micrococci resembling the swine-plague germ but had 
no effect on a rabbit inoculated therewith. To test virulence of the svvine-plaguo 
bacteria isolated on agar plates from lung and spleen, bouillon cultures inoculated 
fi;om colonies on the plates were injected into two rabbits snbcutaneously, each re- 
ceiving one-eighth cubic <'entimetre. Both were dead iiext day. In the organs were 
swine-plague germs in large numbers. The same germs obtained in culture from 
these rabbits. 

Gelatine roll cultures made from these bouillon cultures failed as usual to develop. 
No. Iti. Female pig, weight from 75 to 80 lbs. Died at noon, August 4 ; examined 2 
hours later. General condition of body good. On ventral surface along median 
line and on left fore-limb, slightly elevated scabs one-half inch in diameter. Ex- 
tensive serous infiltration of superficial muscular tissue of ventral aspect of neck 
and sternum and of muscles under scapula, extending along the muscles of the left 
limb as far as the toes. The limb is very much swollen, the skin bluish red. Sub- 
cutaneous lymph glauds of groin enlarged, firm, and pale, mottled with red lines and 
streaks. 

Spleen enlarged, dark, and soft. The fat of the mesentery dotted with petechias. 
Digestive tract: One ulcer on left margin of tongue. The fundus of stomach has 
its mucosa thrown into small folds and deeply redden<'d over an area of about 8 inches 
in diameter, the hyperaemia being most intense on the periphery of this area. About 
3 inches from the pyloric valve an area of necrosed tissue 3 inches long and 1 inch 
wide, the slough blackish, involving the entire mucous layer and one-eighth to one- 
fourth inch thick. Lymphatic glands on lesser curvature with hemorrhagic cortex. 
Mucosa of duodenum deeply pigmented, the pigmentation beginning abruptly at 
the valve and extending with variable intensity throughout the entire small intestine. 
Mesenteric glauds with cortex much reddened. 

Contents of large intestine of an earthy character, more or less adherent to the 
mucous membrane. Mucosa of ca'cuni and colon of a pale slate color. In the rectum 
a considerable number of somewhat faded imnctiform extravasations on a pale mu- 
cosa. In cajcum, 2 inches from valve, one ulcer, one-half inch in diameter, with super- 
ficial, pultaceous slough. On Peyer's patch iifcar valve one small ulcer. In the upper 
cohm about 3 inches from valve, an irregular patch of necrosed mucosa, about 2 
inches long, with blackish surface and rather firm, yellowish base one-eighth to one- 
fourth inch thick. In remainder of colon three superficial healing ulcers with easily 
detachable slough. 

Liver enlarged ; interlobular marking appears broadened and pale, the center of 
acini dark red. Parenchyma somewhat softened and hypersemie. No sensation of 
grittiness imparted to knife. Much fat observed in sections of fresh tissue in the 
form of large globules. Cells sharply outlined, nucleus distinct. 

Kidneys show under capsule a small number of petechiae. Organ very pale through- 
out, especially cortex. 

Xai4_^5 •gee page 77, 



e6 

Over both lungs the interlobular tissue is distended witli clear, yellowish serura, 
some in pleural sacs. Parenchyma edematous, not hepatized, with exception of a 
necrotic and cedematous focus near tip of right principal lobe adjacent to large bron- 
chus, which at this point is occluded with adult lung worms. Trachea and bronchi 
contain much foam and yellowish Hakes. BronchiiJl glands enlarged ; some lobules 
with cortex hemorrhagic, others mottled red and pale. 

Heart cavities and valves normal. Left auricle sprinkled thickly with punctiform 
hemorrhages. 

Bacteriological examination : Two agar tubes inoculated with a loop of pleural 
serum remained permanently clear. 

Agar plates from the edematous lung developed on plate A about 150 colonies of 
hacillun ,liuorescens. On plate B one similar colony. A rabbit inoculated with a bit of 
the same material remained unaifected. 

Spleen pulp shows no bacteria on microscopic examination. One agar plate pre- 
pared with a bit of spleen pulp shows growth only around the bit of tissue. The 
growth made up of motile bacilli which resemble hog-cholera bacilli. The notes of 
the comparative studies of these bacilli are reserved for the end of this chapter.* . 
A tube of bouillon inoculated from the spleen remained clear. 

Liver tissue shows no bacteria on microscopic examination. Two agar plates pre- 
pared with a bit of tissue remain sterile. A tube of bouillon inoculated in the same 
manner became clouded with a short, thick, non-motile bacillus. Agar plates from 
one kidney likewise negative. 

Pig No. 17 died August 5, in the morning, and was examined soon after. Female, 
weighing about 40 pounds, and in good condition. 

The subcutaneous lymph glands in the groin are enlarged and reddened, in part 
hemorrhagic. In peritoneal cavity, a considerable quantity of straw-colored serum. 
The serosa of large intestine roughened and covered by shreds of exudate. A con- 
siderable mass of gelatinous exudate between layers of mesocolon. Mesocolic 
glands swollen, very hypencmic. Spleen very large, dark colored, friable (11 by 3 
by i inch). 

Digestive tract : Stomach partly filled with a thick pea-soup like liquid. Fundus 
over an area of 4 inches in diameter, deeply congested and swollen. A few ascar- 
ides in stomach. The mucosa of ileum sprinkled with numerous punctiform hemor- 
rhages. The caecum appears as an enormously enlarged, dark, bluish-gray body, the 
color being due to diffuse blood extravasations. To it are adherent several coils of 
small intestine and of colon. It is impossible to separate these parts, the adhesion 
being due to extensive inflammatory deposits. The wall of csecum shows great 
thickening; in several places it is H inches thick. The mucosa of Ciccum and 
upper colon sprinkled with large numbers of ochre-yellow excrescences about one- 
fourth inch apart, and from one-eighth to one-half inch in diameter. These are read- 
ily pulled away from the membrane, some leaving but a faint depression, others a 
roughened spot behind, surrounded by a bluish-red zone. The larger the excres- 
cences the deeper the necrosis beneath them. The mucosa is in general of a dirty 
slate color, faintest in the rectum. 

Lungs normal with following exceptions : An area of collapse 1 inch square in right 
cephalic lobe, and a small area on diaphragmatic surface of right ))rincipal lobe about 
one-half inch square showing consolidation beneath. Bronchial glands and those at 
base of heart with cortex hemorrhagic. Air tubes free from mucus and lung wornis» 
A considerable quantity of serum in heart-sac. Epicardinm is covered with a very 
delicate exudate and is thickened and roughened. Ecchymoses on left auricle and eu- 
docardinm of left ventricle. 

Liver not markedly changed ; bile very thick and flaky. Parenchymatous degenera- 
tion of cortex of kidneys. Some petechiaj on pyramids and in pelvis. 

Bacteriological examination : From the pericardial exudate one agar and one 

* See page 77. 



67 

bonilldii tube inoculated with platinum loop. Both remained st( rile. Similarly 
two tubes inoculated with peritoneal exudate remained sterile. Aj^ar plate cultures 
from the spleen which showed no j,'ernis on microscopic examination were made by 
addiuj; to tube A a bit of spleen pulp, to B three loops from tirsfc tube. Plate A de- 
veloped one colony made up of micrococci. On plate B one colony made up of bacilli 
appeared. A bouillon culture made at the same time with bit of spleen pulp became 
clouded and contained a larj^e spore-bearing bacillus and a micrococcus. This was 
plated, but only one colony developed made up of cocci. A rabbit inoculated at same 
time from liouillon reuuiined unati'ected. From the liver agar plates remained sterile. 

The important ])atli()losical changes found in these 17 cases varied 
greatly from animal to animal. In some cases the lungs were uiost 
severely involved, in others the lesions in the large intestine must be 
regarded as most important. In this respect this outbreak differs very 
decidedly from the two preceding ones, in which there was more or less 
uniformity observable. Besides the respiratory and digestive tracts, the 
lymphatic glands and the serous membranes were most frequently in- 
volved. In the glands tumefaction with hypenomia and hemorrhage was 
quite common. In the lungs the appearance of the hepatized regions 
varied considerably. In some necrotic changes had already appeared. 
The following synopsis of the lesions will serve to illustrate the state- 
ments made : 

No. 1. July 21, 1H90. Pneumonia of left lung with exudative pleuritis. Hypencmia 
of stomach; diphtheritic inllamniation of large intestine. Lymphatic glands hyper- 
:«mic and heuuirrhagic. Spleen very large. 

No. 2. Double serous pleuritis. Large intestine hypertemic and pigmented. Sev- 
eral ulcers. 

No. 3, Pueumoniaof right lung with necrotic masses; pleuritis, pericarditis. Ulcer- 
ation of upper large intestine. 

No. 4. Pneumonic foci in both lungs; pleuritis. Hyi)eriemia, pigmentation, and 
ulceration of large intestine. More or le.ss blood extravasation in lymphatics. 

No. .'S. July 22. Double serous pleuritis with interlobular oedema of luugs. No 
hepatization. Hemorrhagic intlammation of stomach ; similar intiammatiou of large 
intestine with superficial necrosis of mucosa. 

No. 6. Killed; examination negative. 

No. 7. Hemorrhagic lymphatics; subserous hemorrhages in abdomen. Lungs and 
digestive tract not atfected. 

No. 8. Extensive hepatizatioTi of b'oth lungs ; ])igmentation of large intestine. 

No. 9. Spleen large. Scattering pneumonic foci ; lung worms. Hyperiemia of large 
intestine. 

No. 10. Partial hepatization of lungs with interlobular (edema and serous pleuritis. 
Lymphatics hemorrhagic. Hypera3mia and superficial necrosis in large intestine. 

No. 11. July 28. Extensive hepatization of lungs with double plastic pleuritis. 
Hyper:T5mia of stomach. Diphtlioritic iullanimation of large intestine. Lymph glands 
hvpera>mic and hemtu'rhagic. 

No. 12. Anterior small lobes of lungs hepatized; no pleuritis. Peritonitis. Hem- 
orrhagic inflammation of a portion of small intestine. Pigmentation of large intes- 
tine ; indurated ulcers present. Lymph glands hemorrhagic. 

No. 13. July 31. Partial hepatization of lungs with necrotic foci; pleuritis; 
bronchitis; peritonitis. Hypenemia of large intestine; ulceration .slight. 

No. 14. August 4. Gelatinous a?dema of left fore limb. One-half of lung tissue hep- 
atized with many necrotic foci; pleuritis. Hemorrhagic inflammation of stomach. 
Ulcers in large intestine 



68 

No. 15. Atelectasis of several lobes of lungs ; no hepatization ; bronchitis. Hem- 
orrhagic inflaminatiou of stomach. Extensive ulceration in large intestine. 

No. 16. Extensive oedema of left fore limb. (Edema of lungs. Serum in both 
pleural sacs. Bronchitis. Lung worms. General swelling of lymph glands. Hyper- 
ajmia of stomach with localized necrosis. Pigmentation and discoloration of small 
and large intestines. A few ulcers in tlie latter. 

No. 17. August 5. Lungs nearly normal. Pericarditis. Peritonitis. Hyperasmia 
of stomach. Enormous inflammatory thickening of csecum with deposits around it. 
Spleen large. Lymph glands swollen, hypersemic. 

The important question arises as to the true nature of this disease. 
To the writer it appeared at first like hog cholera, possibly like a mixed 
outbreak of hog cholera and swine plague. The bacteriological in- 
vestigations, however, did not confirm this opinion, based on the post- 
mortem appearances. As the investigation proceeded hog-cholera 
bacilli failed to appear in the cultures with certain excei)tions to be 
discussed farther on, and indicated in the following table as motile 
bacilli : 



Case 

No. 


Lnngs. 


Pleura. 


Spleen. 


Liver. 


Kidney. 


e 

6 
7 
8 
9 
10 
13 

14 

15 

16 
17 




Negative 


Negative 








...do 


Negative 








...do 


....do 








....do 










Swine plague- 
Negative 

S wine-plague. 








Negative 

Swine plague. 

Negative 


Swine plague. 
(Peritoneum) 
swine plague. 


Swine plague. 


Swine 
plague. 

Negative . 

Swine 
plague. 

Negative . 




Swine-plague 
and motile 
bacilli. 

Motile bacilli 
(bog chol- 
era?) 


Swine plague . 

Negative 

...do 


Negative 

....do 

(Peritoneum) 
negative. 


Negative 

(Pericardium) 
negative. 









It will be noted that in the eleven cases bacteriologically examined 
swine-plague bacteria appeared in only four. In these four cases they 
were detected in nearly all organs subjected to examination. Why they 
were not found in all cases may be due to several reasons. In the hrst 
place, former experience has shown that swine-plague bacteria are apt 
to remain localized, and that dissemination through the body does not 
always take place. If limited to the digestive tract they could not have 
been detected, because this was not subjected to examination. Secondly, 
swine-plague bacteria are short lived, even in cultures. They may have 
largely disappeared from the body at the time of death. Moreover, it 
is not improbable that many swine die from the secondary effects of the 
disease. (See No. 17.) The time of examination is therefore of import- 
ance. Swine may be infected all together within a short time, and the re- 
tarded deaths may be due to partial resistance followed by complica- 
tions. The lesions produced in the lungs and intestines may permit 
otlierbacteria to enter the body, which complicate still more our under- 
Standing of the real cause, 



69 

While therefore the bacteriological results were meager, the inocula- 
tion experiments and one experiment in which pigs were exposed to the 
disease were snccessful in demonstrating conclusively the pathogenic 
power of the swine-plague bacteria obtained from this outbreak. 

EXPOSURE EXPERIMENT. 

The experiment in which healthy station pigs were exposed to those 
sent from Fleasantville in the same pen is particularly interesting. 
Five Station pigs (Nos, 383-387) were placed in the pen with the five 
infected pigs (Nos. 13-17). The period of exposure varied greatly, as 
may be seen from the table below. Nos. 384 and 385 received a thor- 
ough exposure so fiir as regards contact with the si(;k pigs. No. 383 a 
l)artial one, and Nos. 386 and 387 were placed in the infected pen only 
after all the sick and infected had died. 



No. 


July 29. 


July 30. 


July 31. 


Aug. 1. 


Aug. 2. 


Aug. 3. 


Aug. 4. 


Aug. 5. 


Bacteriological 
result. 


13 

14 

15 

Ifi 
17 


X 

X 
X 

X 
X 


X 

X 

X 

X 
X 


Dies . . 












SwiiiP- plague 
ba(;teri:i. 

Negative. 

Swiue-pl ague 
bacteria. 

Negative (hog- 
cholera bac- 
teria?) 

Negative. 


X 

X 

X 
X 


X 

X 

X 
X 


X 

X 

X 
X 


X 
Dies 










X 
X 






X 


Die.s . . 


383 

■.m 

.(86 

387 












Exposed . . 
X 
X 


X 
X 
X 


X 
X 
X 


Dies August 9 of 

.swine i)lague. 
Expoaed Aug. 9. 


Exposed.. 
....do 


X 
X 


X 

X 


X 
X 


X 
X 



































The result of this exposure was the death of No. 385 of swine plague. 
In the lungs were disseminated numerous hepatized foci undergoing 
necrosis. There was considerable plastic pleuritis matting the lobes to- 
gether. In the digestive tract extensive hypersemia bordering on 
hemorrhage. Swine-plague bacteria were obtained from the lungs, 
l)leural exudate, heart's blood, and large intestine. Cultures were also 
made from the spleen, liver, mesenteric glands, and kidneys, to make 
sure that if hog-cholera bacteria were present they should not be over- 
looked, but none could be found. A clearer demonstration of the disease- 
l)roducing power of swine-plague bacteria could not well be obtained. 
The importance of this case warrants the publication of the notes in 
detail: 

No. 385. Black Essex grade, aged 3 months, placed in pen containing Nos. 13 to 
17, inclu.sive, on July 29. Found dead August 9, rather unexpectedly, after a sickness 
lasting but 2 days, and manifested by dullness and refusal to eat. 

Examined a few hours after death ; kept on ice in the meantime. As the skin is 
reflected, the cut subcutaneous blood vessels discharge drops of dark blood. In ab- 
dominal cavity nothing abnormal. Pericardium thickened, opaque, vessels injected. 
Left half of heart iirmly contracted. Ecchymoses on the right auricle. Right side 
contains a pale clot imbedded in a dark coagulum. 



70 

Respiratory tract: Mucosa of larynx and epiglottis congested. Mucosa of traclioa 
covered witli a very thin layer of translucent, very viscid mucus. Broneliial glands 
enlarged, pinkish on section. Costal pleura of the right side discolored, thickened, 
overlaid by a soft grayish exudate ; its blood-vessels injected. Diaphragm similarly 
affected. The various lobes of the lungs lightly glued to one another aud to the peri- 
cardium. Considerable pleuritic exudate on the right ventral and along the edges of 
both principal lobes. Lungs in general hypera'Uiic. Left ccphali(5 lobe ompliysema- 
tous ; left ventral shows hemorrhagic spots near its tip and contains two firm nod- 
ules, appearing as yellowish spots under jileura. Left princi])al lobe contains four 
of these sjjots C()rres])oudijig to firm nodules in the parenchyuja. Besides these, a 
Avedge-shaped, very tirni, hepatized mass extends inward from (he edge and almost 
through the depth of the parenchyma. These various masses a|»i)ear yellowish, homo- 
geneous, imbedded in hypera'Uiic, air-containing tissue. They vary from one-eighth 
to five-sixteenths inch in diameter, nearly all of them situated near the surface. The 
largest ones are covered by roughened, thickened pleura, thrown into wrinkles; these 
are in part yellowish, in part bright red and pink in color. The three lobes of the 
right lung contain these necrotic masses. There are several in the right cephalic, 
about six iu the ventral, and over a dozen in the principal lobe, the largest being 
one-half inch in diameter. 

Digestive tract: Several small superficial sloughs on dorsum of tongue, uear tip. 
Stomach contains a considerable quantity of food. Fundus deeply reddened over au 
area 5 inches in diameter. Duodenum with its mucosa bluish-gray, pigmented. Pey- 
er's patch showing as an aggregation of small, depressed pigment spots. Arbores- 
cent injection of jejunum merging into a geueral hypera-mia lower down. About 18 
inches above valve a patch of mucosa 2 inches long, intensely reddened. 

Extensive pigmentation of mucosa of c;ecum. Mucous glands at the valve dis- 
tended with plugs. About 12 inches below the valve the mucosa is intensely red- 
dened, merging on hemorrhage. A very delicate elastic membrane (fibrin?) covers 
this region, extending for about 12 inches down the colon. Below tins latter point 
the mucosa continues more or less hypera-mic and pigmented into the rectum. Mes- 
enteric glands enlarged with cortex and interlobular i>ortions hemorrhagic. Meso- 
colic glands iu the same condition. 

Kidneys with cortex pale, somewhat enlarged. Otherwise uo marked changes ob- 
served. 

Spleen slightly enlarged and softened. 

Bacteriological examination includes the following organs: 

In two necrotic foci of the lungs examined a number of minute oval bacteria with 
pidar stain were observed in cover-glass prei>arations. Plates prepared with a bit of 
this tissue remained sterile, however. A rabbit inoculated subcutaneously with a 
hit of necrosed lung tissue at 15 p. m., Aug. 9, was found dead next morning. In the 
spleen and heart's blood aud iu cultures therefrom only swine-plague bacteria de- 
tected. The cultures were inclined agar and bouillon. 

In cover-glass preparations of pleural exudate, a large number of swine-plague 
bacteria were detected. Two inclined agar and one bouillon tube inoculated at the 
autopsy. One agar remained sterile, the two other tubes developed into pure cul- 
tures of swine-plague germs. 

From the spleen agar plates prepared with a bitof pulp remained sterile. Abouil- 
irm culture contained H large spore-bearing bacillus. From the liver, the same prep- 
arations made. Both plates and bouillon remained sterile. 

From the contents of right ventricle two agar and one bouillon tube were inocu- 
lated after scorching through the wall. The bouillon tube remained clear. Both 
agar tubes contained subsetjuentiy a grayish glistening growth of swine plague 
bacteria. 

From a mesenteric gland one agar and one bouillon tube inoculated by scorcliiig 
the surface and removing witii small scissors bits from beneath this area. Both tul)cs 
remained sterile. 



71 

From ono kidnoy two agar plates and a bouillon tiihc jncpnrcd. Plate A was 
spoilt by an extensive surface growth. On Plato 11 abont 12 colonies developed, 
some made up of micrococci, some of bacilli. The bacilli on plate B were examined 
more closely and readily ditt'erentiatod from hog-cholera bacilli {IhicUIhh coU vominunis) 
in gelatine rolls and subcultures therefrom. The 1)ouillon cuUurc contained a large 
spore-bearing bacillus. 

From the hyperiemic mucosa of colon iigar plates were made, which, howevon 
gave no information as to the presenc<! of swine-pLigue bacteria. A rabbit was in- 
oculated by injecting unihsr the skin a lew drops of scraf)ing fiom the colon stirred 
U[) in sterile water. Ral)bit lound dead on the second morning. In cover-glass prep- 
arations and cultures from blood and spleen only swiur-plague bacteria detected. 

The four remaining' pigs did not (He, but they were ill for a time and 
remained in a very unthritcy eondition. They were killed about three 
mouths after exposure. No pathological changes were observed with 
the exception of slight hyi)eraMnia in the duodenum and a few small 
areas of collapse in the lobes of the right lung of 381, and bronchitis and 
colla[)se of the entire right cephalic lobe in 380. In 387 the solitary 
follicles of the colon were swollen ; from some a curdy mass could be 
exi)ressed through a central dei)ressed opening. 

INOCULATION OF SWINE WITH 8WlNi)-PLAGUE BACTERIA FKOM THIS 

OUTBREAK. 

Besides the successful production of disease by simple contact with 
diseased animals, a considerable number of inoculations upon pigs were 
made, the earlier ones to test tlie i)athogenic power of these bacteria, 
the later ones in carrying out vaccination experiments. Only a i)()rtion 
of them are given below : 

On October 30, two ])ig8 (Nos. 399 and 404) were fed the chopped viscera 
of six rabbits \vhich had been inoculated subcutaneously on the ])reced- 
ing day and had all succumbed during the night. The viscera, which 
contained immense numbers of swine-plague germs, were readily eaten 
after being mixed with a small quantity of feed. The pij?s remained 
well. 

On the same <lay the following inoculations were made: 

Pig No. 402 re(!eived a subcutaneous inje(^tion of 5.^ cubic centimetres 
of a peptone bouillon culture of swine-plague bacteria L'4 hours old, 
one-half injected into each thigh. 

No. 400 received into a vein of the leg 1 cubic centimetre of the same 
culture. 

No. 403 received into a vein of the leg 5 cubic centimetres of the same 
culture. ■• 

No. 401 received into the right lung, through the chest wall, 5 cubic 
centimetres. 

The.se pigs were black pigs (Essex and Berkshire crosses) about 3 
mouths old. The bacteria originally derived from case 15 had been 
passed through a number of rabbits and guinea-pigs since August 3. 

No. 402 showed no signs of disease after the inoculation. No. 403 



72 

died first. The inoculatiou took place at 3:30 p. ra., October 30, and 
the animal was found rigid at 6:30 next morning. 

General blush of the skin on the ventral aspect of the borly. On right side the 
small vessels of the subcutis filled with blood which oozes from the cut ends in the 
form of thick drops. Both superficial inguinal glands hypericmic. 

A small quantity of yellowish serum in the abdominal cavity. A network of 
delicate fibrils stretching across coils of intestine. Peritoneum dnll, opaque in ap- 
pearance. 

Trachea and bronchi contain reddish froth, mucosa reddened. Punctiform hemor- 
rhages under the pleura of left lung. Slight general ajdema of both lungs ; some 
interlobular oedema of the right. 

Stomach contains a moderate quantity of deeply yellow-colored liquid. The 
mucosa covered with a thick layer of tenacious mucus. The fundus over an area 8 
inches in diameter is intensely hyperaemic, the intensity being greatest in the center 
of the area. Contents of duodenum of a blackish color. More or less hyperaemia 
throughout the small intestine, with swelling, hyperiemia, and ccchymosis of Peyer's 
patches. More or less hyperaemia in patches in the caecum and colon. The glandular 
liatch at the valve especially reddened. Feces dry. Follicles show as circular, red 
spots from the serous side. Lymphatic glands of the lesser omentum, mesentery, and 
meso-colon very much reddened. 

Liver congested. Bile thicker and darker than normal. 

On surface and throughout the cortical portion of kidneys numerous punctiform 
hemorrhages. Pyramids intensely congested. Glands at hilus with cortex hemor- 
rhagic. Bladder contracted, empty. 

No. 401 died in the evening of October 31, i. c, somewhat more than 
24 hours after inoculation. It was placed in large refrigerator until 
next morning. 

Subcutaneous vessels as in No. 403. Small patches of a grayish, viscid exudate on 
the large intestine, liver, and spleen. Punctiform ecchymoses barely visible to 
naked eye under serosa of large intestine. Arborescent injection of the subserous 
vessels on ventral wall of abdomen and intestines generally. 

In the right pleural sac a considerable quantity of blood-stained liquid and shreds 
of exudate stretching from lung to chest wall. The various lobes of both lungs 
glued together and to pericardium. The lateral, ventral border of both lungs have 
the pleural covering much thickened, roughened, and thrown into wrinkles. Both 
lungs congested and oedematous. In the right cephalic lobe a mass of dark red 
hepatized tissue which may be the place where needle punctured. Grayish-red 
hepatization of the major portion of left cep'.ialic lobe. Trachea and bronchi contain 
a large quantity of reddish foam. Mucosa with minute vessels injected. 

Pericardium opaque and roughened. The entire epicardium similarly affected. A 
grayish membranous exudate about the base of the heart extending xipon the large 
vessels. 

Stomach contains a moderate quantity of turbid, saifron-colored liquid; mucosa 
covered with a thin layer of mucus. Punctiform reddening of fundus. Small intes- 
tine contains much yellowy liquid, mucosa not altered. Large intestine contains 
firm feces. No lesion s'observed. 

Cortex of kidneys rather pale, pyramids very dark red. 

Under capsule of spleen, some small extravasations. Parenchyma pale, organ not 
enlarged. * 

Cover-glass preparations from peritoneum of small and large intestines and of liver 
show many swine-plague bacteria. In the spleen their presence not determinable on 
cover-glass preparations. Cultures contained them, however. 



73 

N"o. 400 became very sick oji the day followinii,- the inoculation. It 
was uuable to rise and showed si<?us of distress when disturbed. It 
continued to lie quietly until November 3, when it died at noon, about 
4 days after the inoculation: 

Animal in very good condit.ioa ; almndance of snbcntaiif^ous fat. Blood vesseLs of 
aubcntis as in preceding cases. In abdominal cavity nothing abnormal. 

Don1>le plenritis with adhesion of varions lobes of Inngs to each other, to chest 
wall and pericardinm. Grayish membranous exudate over the ribs on the right side. 
The subjacent pleura has a blnish appearance. The corresponding pleura of lung 
covered by patches of similar exudate. Tlie right lung dark red throughout but not 
hepatized. In the left lung the ventral third of the ventral lobe is dark red, solid; 
on section granular and interspersed with grayisli areas. The lateral edge of adjacent 
principal lobe is likewise hepatized for a distance of 1 inch inward and ;:i inches along 
border. 

Pericardium thickened, opaque, roughened; blood vessels injected; entire epicar- 
diuin covered with a rather thick fals(! membrane, loosely attaching the perittardinm 
to it. Large quantity of dark, partly coagulated blood in right lieart; a very little 
in the left heart. 

Stomach empty, lined with a thin layer of bi.le-staiued mucus. In the lower ileum 
several patches of mucosa of a dark bluish color, each about 6 inches long. Large 
intestine filled with dry, firm feces. In the upper colon, mucosa is 8late-C(dored, 
lower down normal in color. 

Liver rather firm, surface appears slightly roughened and mottled, owing to conges- 
tion of individual lobules. These deeply reddened lobules disseminated through 
whole parenchyma. Hepatic vessels contain much thick dark blood. 

Kidneys considerably enlarged, the surface besot with a Uirge number of grayish, 
slightly elevated spots, some surrounded by a dark-red zone. They vary from one- 
half to one-fourth inch in diameter and are about one-fourth inch apart. On sec- 
tion they correspond to grayish wedge-shaped masses extending inward through 
the cortex and in the form of longitudinal stri.-u through the pyramids to the i>apill;i'. 
These infarcts are made up, examined fresh, chietly of pus corpuscles. 

Only the spleen of this case was subjected to examination. No germs were seen in 
cover-glass preparations, but they were obtained in cultures. 

Sections were prepared from the hepatized lung tissue hardened in alcohol and 
stained with alum-carmine and methylene hlofi. The alveoli were found completely 
occluded with cellular masses partaking chiefly of the character of leucocytes. The 
red blood corpuscles were i)resent in small numbers. Fibrin not detected. The 
alveolar capillaries distended with red corpuscles projecting into the lumen of the 
alveoli. In the coll nuisses swine-plague bacteria are very abundant. They are 
scattered between the cells, not in clumps. 

Sections from the kidney hardened in alcohol and stained with methylene blue 
showed the cellular infiltration in the cortex and extending through the medullary 
portion in the form of cylindrical cell masses occupying the lumen of the large col- 
lecting tubules which are completely stripped of their epithelium. Swiue-plaguo 
bacteria are disseminated through these cell masses as in the lung tissue already 
described. 

The foreg'oino- notes indicate that 5 cubic centiilietres of a i)ei)tone 
bouillon culture of swine-plague bacteria injected into the circulation or 
the lungs may be fatal within 24 hours. They also show a tendency to 
indammation of the large serous cavities, especially the pleural, even 
when the injection is made into the circulation. This inflammation cor- 
responds closely with that found in the disease as it occurs in nature. 



74 

Auotber important fact is tlie production of pnonmonia not only when 
the bacteria are injected into the lungs, but when introduced into the 
circulation. 

Feeding and subcutaneous inoculation failed to produce disease. 
That the latter will now and then produce disease is well shown by the 
following case: 

Pig No. 454 was inoculated February 28, 1891, with a i)eptoue bouillon 
culture of the swine-plague germ from Case 15. Three cubic centimetres 
were injected subcutaneonsly into each thigh. The culture was one 
day old, i)repared from an agar culture. (Three others inocnhited at 
the same time remained well.) The pig was found dead March 2, in the 
early morning. It had thus lived between 3G and 48 hours after the 
inoculation. 

Black and red female pig, weigliing about 50 pounds; in good condition. Consid- 
erable reddening of the skin of ventral aspect ol body and ears. Subcutaneous fat 
reddened. From the cut vessels dark, thick blood exudes. Over both inoculated 
thighs the subcutaneous vessels are extensively injected, forming a dense network. 
The subcutis has a glistening appearance. On the right thigh, near Poupart's liga- 
ment, the subcutaneous connective tissue is thickened, yellowish opaque, and friable, 
over an area of several square inches. 

On opening abdomen the intestines appear very much reddened. A few elastic 
fibrils stretched across coils and about 10 cubic centimetres of turbid serum present. 

Stomach contains a large quantity of food. Mucosa not aifected. Considerable 
catarrhal inflammation of the duodenum, which extends into jejunum. The hyperje- 
mia extends through the snuill intestine, but much less intense. Several ascarides 
present. The mesenteric glands somewhat congested; in two of them old, caseous 
masses, occupying nearly the entire gland. 

Large intestine contains a large quantity of semiliquid feces. Mucosa normal. 
Meso-colic glands hyper«mic. 

In each pleural sac about 10 cubic centimetres of turbid effusion. Lungs hyper- 
ajmic and tcdematous. Interlobular tissue of anterior (or cephalic) lobes slightly 
thickened and opaque, the result of some former inflammation. In trachea and 
bronchi some reddish frothy liquid. The mucosa shows marked injection of the 
minute blood-vessels, in some places almost hemorrhagic. In right bronchus a small 
number of large lung worms. 

On left auricle of heart ecchymosea. In left ventricle a small quantity of rather 
thick dark blood. Right veutricle distended with it. Coagulation feeble. 

Liver quite pale generally, acini distinctly outlined. Parenchymatous inflamma- 
tion. On the surface may be seen with a hand-lens numerous minute grayish-yellow 
dots, one or more in a lobule and situated chiefly on the periphery. In sections of 
fresh tissue they appear as irregular, opaque, amorphous patches. In stained sections 
from tissue hardened in alcohol they appear as intralobular aggregations of round 
cells occupying the place of parenchyma cells. These foci are probably result of 
some former disease. In the intralobular capillaries occasional masses of swine- 
plague bacteria detected. (See PI. xi. Fig. 4.) 

Spleen enlarged and hypera^mic. Kidneys with cortex broadened. The base of 
pyramids somewhat darker red than normal. 

In cover-glass preparations from blood and spleen, swine-plague bacteria present, in 
the blood in considerable numbers. 

From a bit of spleen pulp two agar plates prepared. On the first, after 24 hours, 
numerous swine-plague colonies appeared; on the second nothing developed. 

Agar cultures from peritoneal and left pleural cavity remained clear. 



75 

Au a-ar tube inoculated from the blood contained a large nnn.ber of conllnout 
colouier. A bouillou tube became faintly clouded. Both contained ouly swiue-plague 

bacteria. . . ^ • , j.i „ <•„! 

An agar culture from the liver inoculated with platmum wire contained on the toi- 
lowing^day a considerable number of swine-plague colonies. 

Two of the following cases are of importance owing to the peculiar 
lesions of the joints caused by the inoculation. 

November 11. With a peptone bouillon culture of swine-plagne bac- 
teria from the same stock culture (Case 15) the following inoculations 
were made: Nos. 405 and 408 received into a vein of one hind leg one- 
half cubic centimetre; Nos. 400 and 407 received one-fourth cubic centi- 
metre. In each case the quantity was diluted with sterile bouillon so 
that 1 cubic centimetre of liquid was injected. 

For the two following days all pigs were sick and refused to eat the 
food set before them. Within a week Nos. 406 and 408 had nearly 
recovered, No. 405 partially, while No. 407 was unable to get up and 
continued so until it was killed, December 3, by a blow on the head. 
Its chief lesions were a peculiar necrotic and suppurative condition ot 
the joints and suppurative pericarditis. 

Con.lition of animal very poor. Enlarocment of the left carpal and phalangeal 
ioints of the right elbow ioint, and both hock joints. Along the inner .t^pect of the 
left sc'apnla, large masses of yellowish dry pus deposited around the muscles. Carpal 
ioint of the same limb much enlarged. On openiug the joint a considerable qnant.ty 
of dry pus is found deposited around the bones and between the ten.lons over the 
ioint The joint surfaces are discolored, the cartilages in part detached, and the 
small bones readily crushed. The toes enlarged, the enlargement due to similar sup- 
purative changes around the phalanges. , ^, • • . 
Rioht elbow joint enlarged; joint cartilages greenish, opaque. Around thejmnt 
seve^il abscesses containing either a turbid liquid or dry cheesy pus, which has bur- 
rowed along the intermuscular septa of the forearm. Carpal and metacarpal joints 
of this limb not affected. 

On both hind limbs the tarsal and metatarsal joints very much enlarged and in the 
same condition as those just described. In a small number of ribs the sternal articu- 
lation involved in suppuration. Over the lower ribs on the right side the intermus- 
cular septa are imbedded in masses of dry cheesy pus. 

Within the lymphatic glands at the angle of the jaw and in the inguinal region are 
minute yellowish masses. 

Lun-s normal. Pericardium thickened, adherent to the heart surface by means ot 
a laver of brittle, straw-colored pus, covering the entire heart surface with exception 
of a small area on the left ventricle, to which the pericardium is attached by means 
of delicate fibrous tissue. The pus is most abundant at the base. 

The digestive tract free from inflammatory changes. Ston.ach contains a small 
quantity "of liquid of a deep yellow color, and some mucus. 

Kidneys show on the surface a small number of discolored, slightly depressed spots, 
corresponding to pale, whitish, wedge-shaped infarcts, extending into medullary 

^'"^Uvev discolored in spots and patches on the surface. These also seen in sections. 
Gall bladder contains a dark-greenish solid mass, cutting like iirm cheese and lill.ug 
up the entire space of the bladder. 

One tarsal joint saved and opened for bacteriological examination 1 he skin .s 
removed, the sac of the abscess thoroughly sc.u-ched and opened through the scorched 
area with a flamed knife. A considerable quantity of greenish-yellow liquid holding 



76 

in suspension brittle masses of pus wells ont. From tins liquid one inclined agar, one 
bouillon tube, and three agar plates prepared. The agar and the bouillon tube con- 
tained active growths of the injected swine-plague germ. Ou the first agar plate 
an immense number of minute colonies appeared; on the second about two hundred, 
and on the third very few. From these plates all colonies examined were made up of 
swine-plague bacteria. 

A rabbit inoculated subcutaneously with a particle of the pus died within 20 hours. 
In cover-glass preparations from liver and spleen, and in an agar culture from the 
latter organ, swine-plague germs demonstrated. 

Anotlier case of suppurative changes in the joints following intra- 
venous inoculation is the following: 

No. 411 received, December 4, IJ cubic centimetres bouillon culture of swine- 
plague bacteria into a vein of one hind limb. It immediately became very sick, was 
unable to get up, and died December 22. It was greatly emaciated. Both carpal 
and the left tarsal joint enlarged, the changes within the joint similar to those 
described in the preceding case. Several rib joints in the same condition. In this 
case also the presence of the virulent swine-plague bacteria in one diseased carpal 
joint was demonstrated by inoculating two rabbits with pus therefrom. Both suc- 
cumbed within 20 hours to the inoculation. In the organs the characteristic polar- 
stained bacteria. An agar and a peptone bouillon culture from the spleen of the pig 
remained sterile. 

Two other pigs inoculated at the same time aud with the same dose 
died in 15 hours with commencing peritonitis, pleuritis, and pulmonary 
oedema. In both the stomach was hyperaemic. 

PATHOGENIC EFFECT ON SMALLER ANIMALS. 

The great virulence of the swine-plague bacteria from this outbreak, 
as compared with those of former outbreaks, is even better shown by 
the inoculation of small animals. In the notes given below ifwill be 
seen that not only rabbits but guinea-pigs aud pigeons succumb to very 
small subcutaneous doses of the growth from cultures, while large 
fowls are killed by inoculations into the muscular tissue. The inocu- 
lation of guinea-pigs aud pigeons with cultures from previous outbreaks 
was usually uncertain even though rabbits invariably succumbed. 

Guinea-pigs. — October 2, 1890. One guinea-pig received subcutaneously into the 
thigh one-fourth cubic centimetre of a peptone-bouillon culture of swine-plague bac- 
teria, a second one-twelfth cubic centimetre, and a third one twenty-fourth cubic 
centimetre. The liquid in each case was diluted with 2 parts of sterile bouillon, 
hence 3 times this quantity of liquid was actually injected. 

The second guinea-pig died within 24 hours. At the point of inoculation consider- 
able gelatinous oedema, the blood vessels injected, and the muscles of thigh covered 
with a thin, grayish layer. Stomach and small intestine hyperaemic. Spleen en- 
larged, dark colored. In blood, spleen, and liver very few bacteria. An agar culture 
from the spleen developed only colonies of swine-plague bacteria. The first guinea- 
pig died several hours later with similar lesions. Peyer's patches hyperiemic. A mod- 
erate number of swine-plague bacteria in the various organs. The third guinea-pig 
dieil in about 36 hours with the same lesions. 

October 7. A guinea-pig was inoculated with one one-hundredth cubic centimetre 
of a peptone-bouillon culture. It died in 40 hours. The small intestine very hyper- 
iemic, occasional patches of punctiform hemorrhages in mucosa. A small number of 
bacteria in the various organs not showing a distinct polar stain. 



77 

October 14. Two giiiiiea-pif»8 were inoculated, one witli one one-thousandth cubic 
centiuietro and the other with cue forty-thousandth cubic centimetre of a peplono- 
bouillt>u culture. The first died in :i6 to 40 hourn, the second iu 8 days. In this 
hitter ca.se tlune was considerable jjurukiut tiiickening of the subeutis around the 
phice of injcelion. The intestines, liver, and spleen covered by a thin layer of cellu- 
lar and fibrinous exudate. Very few bacteria in the various organs and the exudate. 

Numerous additional inoculations of very small doses into guiuea-pigs conliruu-d 
the fatal eflectof this orjjjanism on this species of animals. 

Mice. — November 15, 1890. Two gray mice inoculated with one or two drops of 
peptone-bouillon culture died within 20 hours. In the spleen numerous swinc-plaguo 
bacteria which show the polar stain very well in stained preparations. 

Pigeons. — No. 1 inoculated by an injection of 0.3 cubic centimetre of a turbid sus- 
l)ension from an agar culture 24 hours old. The injection was made under the skin 
of one pectoral muscle. Pigeon No. 2 inoculated in the same way with 0.2 ctibic 
centimetre, the needle of the syringe penetrating superticially the pectoral muscle. 

No. 2 died next morning. Parboiled appearance of inoculated muscle. Liver 
remarkably pale and firm. In blood and liver immense numbers of bacteria showin'' 
polar stain very beautifully. 

No. 1 dies in 24 hours. Slight subcutaneous infiltration at point of inoculation. 
Liver in same condition as in No. 2. Considerable hyperajinia of mucosa of duode- 
num and adjoining small intestine. Contents stained reddish. Bacteria not so numer- 
ous as iu preceding case. 

These inoculations having proved successful, two ])igeous were inoculatiid with very 
small doses from an agar culture from pigeou No. 2, throe days old. 

No. 3. Skin over pectoral incised with a lancet and a loop dipped into the culture 
and rubbed into subeutis. 

No. 4. Skin incised and a minute portion on platinum wire rubbed into subeutis. 

Both dead next morning, i. e., withi.i 18 hours. Bacteria abundant as in preceding 
cases. Livers pale an<l firm. 

FowU. — Two adult hens, inoculated in the same manner as pigeons Nos. 3 and 4, but 
Nvith a lilightly increased quantity on the platinum loop, remained uuaHected. 

Two other adult hens were inoculated with the same bacteria from an agar culture 
suspended iu bouillon until turbid, A hypodermic syringe was used and the needle 
passed superficially into the fibers of the pectoral muscle. One fowl received one- 
fourth cubic centimetre, the other one-half cubic centimetre. 

The first died in 24 hours. No local reaction perceptible. The liver is very pale; 
sprinkled over it many whitish points, character not determinable. Intestines nor- 
mal except ca^ca, which have some ecchymoses under serosa. Large number of bac- 
teria iu blood and liver showing polar staining very well. 

The second fowl died in 3t> hours. Liver very pale and sprinkled with ecchynu)ses 
along the course of the superficial vessels. In liver few, in blood large uuiubers of 
the injected bacteria. 

TWO BACILLI ISOLATED FROM THIS OUTBREAK CLOSELY RESEM- 
BLING HOGrCHOLERA BACILLL 

The facts thus far given are suflScieut to prove that in this outbreak 
the swine-plague bacteria were the chief if not tlie only cause of the 
ei)izootic. In the course of the investigations two kinds of bacteria 
were obtained, which deserve special attention owing to their resem- 
"blauce to hog-cholera bacilli. 

Owing to preoccupation of the writer with Texas fever investigations 
the cultures from cases 13 to J 7, inclusive, were made largely by Dr. V. 
A. Moore, assistant iu the li^boratory, and he was directed to pay speci^il 



78 

attention to all motile bacteria having any resemblance to liog-cholera 
bacilli. Four of such were isolated, one from the lung of No. 14, one 
from the spleen of iSTo. 15, one from the spleen of No. 16, and one from the 
kidney of No, 385. These four bacilli the writer subjected to a very care- 
ful examination. Those from Nos. 14 and 385 were found to be iden- 
tical with the common intestinal germ, bacillus coli communis. Tbose 
from the spleen of Nos. 15 and 16 grew very much like hog-cholera 
bacilli on gelatine plates and in rolls. To bring out the differences ob- 
served we will call the bacilli from Case 15 ;/ and those from Case 16 d\ 

In gelatine rolls d could not be distinguished from a parallel roll cul- 
ture of virulent hog-cholera bacilli. The surface colonies of y presented 
a somewhat different type, in that they spread in a thinner layer with 
very thin edges, somewhat like hacUlus coli. They differed, however, 
from colonies of the latter by their very restricted growtb, attaining a 
diameter of only 1^ to 2 millimetres. 

Both caused considerable turbidity of i)eptone bouillon, while viru- 
lent hog-cholera bacilli cause only cloudiness, which very rarely merges 
into a moderate turbidity. These bacilli multiplied therefore far more 
energetically in bouillon than do virulent hog-cholera bacilli. There 
were other slight differences between these two bacilli. Thus, 
while y caused uniform turbidity of the culture fluid, 6 grew more or 
less in clumps, which caused a rapid settling of the growth in spite of 
the motility of the bacilli. AVlien the culture was shaken up numerous 
clumps and flakes rose from the bottom. In the hanging drop these 
bacilli presented a strange appearance. The various clumps, composed 
of 10 or more bacilli, moved rapidly in various directions across the 
field of the microscope. This peculiarity of 6 maintained itself after 
passing through several rabbits and many cultures. In their patho- 
genic power these two bacilli differed not only from hog-cholera bacilli, 
as they are usually encountered in outbreaks, but from one another, as 
the following experiments show : 

Bacillus ;/. Plate cultures made from original culture and bouillon 
inoculated from a colony. When 24 hours old, this culture was used 
to inoculate 2 rather large rabbits. 

One white rabbit received subcutaneously 0.3 cubic centimetre cul- 
ture liquid. 

One black rabbit received into an ear-vein 0.3 cubic centimetre 
culture liquid. 

Two weeks thereafter, neither having shown any signs of disease, 
they were reinoculated. The black one received 1 cubic centimetre, 
the white 0.5 cubic centimetre, both into an ear vein. 

The white rabbit remained unaffected. It was killed after 16 days, 
but no lesions were found. The black one died in 36 hours. The blood 
was thick, tarry; the left lung hypostatic; the spleen small. No 
bacteria in cover-glass preparations from the spleen. This result did not 
place these bacilli above the level of the ordinary intestinal bacteria 



79 

{baciUus coli) \ for 1 cubic ceutimetre of the latter prodncos dcatli in 
rabbits with equal prouiptuess when injected into an ear vein. Two 
additional intravenous inoculations were niade April 2S: 

One rabbit, weighing about 3 pounds, 0.3 cubic centimetre bouillon 
culture. 

Two rabbits, weighing about 4 pounds, 0.6 cubic centimetre bouillon 
culture. 

Both rabbits remained apparently unaffected. 

Finally, on May 21, two rabbits, weigliing each 3 pounds, were inocu- 
lated b3' receiving into an ear vein 0.6 cubic centimetre of a bouillon 
culture. The agar culture had been replated, and Irom a colony this 
bouillon culture was prepared. Neither rabbit showed signs of disease. 

It did not seem worth while to spend any more time on this obviously 
uon pathogenic organism. Its marked resemblance in morphological 
atid biological characters to the hog cholera bacillus makes it highly 
probable that it is closely related to this latter germ. 

Bacillus d. Similar expi'riments with this bacillus from case 16 
l)roved that this one did possess pathogenic i)roperties, though feeble 
in character. 

From the original culture a gelatine plate was prepared and a pep- 
tone bouillon tube inoculated from a colony. When 4 days old two 
small yellow rabbits were inoculated. One received about 0.4 cubic 
centimetre under the skin, the other the same quantity into the ear 
vein. The latter rabbit died in 6 days. 

The spleen is very large, dark, and softened, and contains a large number of 
what appear to be hog-cholera bacilli. The liver shows areas of necrosis. The gall- 
bladder attached by inflammatory exudation to the omentum. The lungs a^dematous. 
Fatty degeneration of cortex of kidneys. The small intestine filled with a glairy 
yellowish li(inid. The cultures from this case containetl only the injected bacilli, 
exhibiting in bouillon tubes the peculiar characters described above. 

The rabbit which received the subcutaneous dose remained apparently uualfected. 
After 22 days it was inoculated with swine plague and fonud dead the following 
morning. At the place of the first inoculation a cyst nearly 1 inch in diameter con- 
taining curdy pus. In the appendix verniiformis from twenty to thirty whitish nod- 
ules under serosa. Similar nodules on Peyer's patch near ileo-ciecal valve. 

A rabbit which received an injection of 0.3 cubic centimetre into abdo- 
men remained well. When killed, 10 days after the inoculation, the same 
appearances of appendix of caecum were found as those just described. 

Several weeks later, with the culture obtained from the first rabbit, 
four rabbits were inoculated, each by an injection^ into an ear vein of 0.2 
cubic centimetre. These all died within 36 to 48 hours. In the one 
which lived 48 hours the following lesions were observed : 

Large, dark spleen. Interlobular network of a yellowish color through the whole 
liver. Under the microscope this appeared as fatty degeneration of the periphery of 
the acini. Lungs cedematous. Left ventricle of heart in advanced fattj' degeneration. 
Cloudy swelling of kidneys. In the spleen large numbers of bacilli which appear 
somewhat larger than hog-cholera bacilli and are usually in pairs. Cultures from 
this case contain only the injected bacilli. 



80 

That the bacilhis S is an attenuated variety of the hog-cholera ba- 
cillus can not be doubted when these rabbit iuoculations are taken into 
consideration. There was, moreover, a gradual increase in virulence 
observed from one inoculation to the subsequent one. Thus the first 
rabbit, which was a small one, received 0.4 cubic centimetre bouillon cul- 
ture into a vein, and lived 6 days. The second rabbit received 0.2 cubic 
centimetre, and died iu 2 days. Subsequent inoculations showed that 
.05 cubic centimetre was fatal in a few days, while smaller quantities 
caused a disease from which the rabbits recovered. 

We have thus seen that in addition to the swine-plague bacteria, 
which produced disease both after inoculation and exposure to diseased 
swine, two motile bacteria were isolated from cases 15 and 10, but from 
no other. These both resembled hog-cholera bacilli very closely, and 
undoubtedly are related to them. But they differed from each other iu 
several particulars, notably in virulence. While the one from No. 16 
was shown to be an undoubted but very attenuated variety of hog- 
cholera bacilli, the one from No. 15, though it may also be an attenu- 
ated variety, has so little virulence that its bearing upon the outbreak 
iu question must be regarded as entirely negative. As to the other 
bacillus the question is not so simple. It may be seriously doubted 
whether it had anything to do iu producing the disease, since its pres- 
ence was detected in but one out of eleven cases, and since hog-cholera 
bacilli from genuine hog-cholera outbreaks appear quite regularly iu 
cultures from the spleen. Moreover, the virulence of the latter is many 
times greater than that of the bacilli iu question. Thus, to test this 
matter thoroughly, one pig received into the lungs 5 cubic ceutimotres 
of a bouillon culture, another 5 cubic centimetres into the abdomen, 
and several others 7 cubic centimetres each directly into the blood. 
None of them showed any signs of illness after such treatment. Lastly, 
two pigs were fed, after a fast of 24 hours, with200 cubic centimetres of 
a bouillon culture each. This feeding was repeated on two successive 
days. A slight diarrhea, lasting a few days, was the only visible effect. 

On the other hand it is not to be denied that these bacilli may have 
occasioned a part at least of the intestinal disease observed in this out- 
break. The truth may be that these attenuated hog- cholera bacilli, 
brought from distant outbreaks by individual animals which have sur- 
vived such outbreaks or proved themselves insusceptible at the time, 
had no effect on the animals brought in contact with them until the 
swine plague broke out, when they may have started into activity and 
contributed to the fatality of the disease. That the bacillus 6 from 
case 16 should have been the cause of the outbreak and the swine-plague 
bacteria secondary to it would seem very far-fetched in the light fur- 
irished by the experiments with the swine-plague bacteria. 

In addition to the attenuated hog-cholera bacilli, another disease 
germ was isolated from cultures prepared on the farni from some of the 
earlier cases. This germ is briefly referred to in the autopsy notes as 
a rather large bacillus, which multiplied in tU© coudeusatioa water of 



81 



agar cultures bat not on the surface. It produces spores which are 
formed in the central portions of the rod. The latter during the de- 
velopment of the spore becomes spindle-shaped. This bacillus does not 
multiply in culture tubes under ordinary conditions, but requires media 
more or less free from oxygen. It belongs to the group of anaerobic 
bacteria, and is probably identical with the bacillus of malignant oedema. 
Whether it is the bacillus which T have frequently detected in swine 
and called '' post-mortem" bacillus it is im]K)ssil)lo to state, since 1 have 
made no special effort to cultivate the latter and test its virulence on 
animals. 

The l)acillus in (juestion grows in deep layers of agar in test tubes. 
The isolated colonies develop quite slowly and after 1 or 2 weeks attain 
a maximum diaiueter of 2 millimetres. The surface of the fully devel- 
oped spherical colony is closely beset with radiating finger-like projec- 
tions, which are perhaps one-fourth as long as the diameter of the entire 
colony. An addition of glucose to the agar favors the growth of the 
bacilli and causes the production of considerable gas, which may break 
up the agar column and force portions nearly out of the tube. This 
bacillus also multiplies in peptone bouillon containing, say, 2 per cent, 
of glucose, provided oxygen is absent. For this purpose the fermenta- 
tion tube, which T have found very useful in bacteriologiciil work, is very 
well adapted.* When such tubes are inoculated a faint cloudiness of 

* The fermentation tube has been in use for many years in various kinds of biologi- 
cal work. Its value in bacteriological work as a culture tube I have already called 
attention to (CeiUralblatt f. Bakterioloijio (181)0) vii, p. 502), but reproduce here a few 

suggestions as to its use. The tube, reduced 
one-half, is shown in the accompanying cut. 
After it has been plugged with cotton wool 
and sterilized in the dry hot air oven it is filled 
with the culture liquid and steamed on three 
successive day.s. The air collecting at the top 
near b, which has been forced out of the liquid, 
should be removed immediately after each 
steaming by gently tilting the tube. After 
the third steaming, the liquid in b is entirely 
freed of dissolved air. The tube is inoculated 
with platinum wire, loop, or pipette as are or- 
dinary tubes. A large number of bacteria, 
especially those living in the intestines of an- 
imals, are capable of setting up a fermentation 
when glucose and other sugars are present. 
The gas collecting at the toj) in b is composed 
chiedy of CO2 and H. 

I have found the fermentation tube very val- 
uable in the diagnosis of hog-cholera bacilli, 
which are capable of fermenting glucose, etc. 
Hog-cholera bacilli from a large number of out- 
breaks tested thus far all manifest tliis phenom- 
enon, and it may be safe to assert that any 
bacilli resembling hog cholera which do not 
produce gas are not hog-cholera bacilli. 
1614 G 




82 

the liquid appears witliiu 1 or 2 days, and gas bubbles rise in the closed 
branch. After a few more days the liquid in the closed branch is in 
part replaced by gas, which continues to form for a week or longer. 
Meanwhile the bacilli have become deposited in the bottom of the tube 
as a whitish, flocculent mass. By cultivation in this way I was able to 
keep these bacilli alive for many months until opportunity offered to 
test them on animals. That they are pathogenic and may cause ma- 
lignant cedema the following inoculations are sufficient to demonstrate : 

May 22, 1891, 3 p.m. From a culture iu a fermeutatiou tube 14 days old one- half 
cubic centimetre of the turbid deposit withdrawn and injected under the skin of a 
rather large guinea-pig iu the region of the abdomen. 

The animal, apparently well at 9 a. m. next morning, lay down at lO.a. m., and died 
at 1 p. ni. On examination very extensive sanguinoleut wdema of the subcutis over 
abdomen and part of thorax. On left thigh the ledema accompanied with much dis- 
tension of the subcutis with gas. The serosa of abdominal cavity discolored and 
vessels injected. Both sides of heart contain dark soft clots. In the blood-stained 
subcutis large numbers of the injected bacilli, in the spleen a few, in the blood none 
observed. Two fermentation tubes were inoculated with blood and a particle of 
spleen pulp, respectively. In both a typical growth appeared in a few days. 

At the same time a colony of these bacilli was removed from a glucose agar tube, 
now 22 days old, and placed into the subcutis of abdomen of another guiiiea-iiig 
through an incision. No symptoms observed until 48 hours, when the animal le.sUid 
with abdomen on floor of cage and did not stir when aroused. Apparently neither 
drowsy nor in pain. It was found dead on the morning of the third day ((iO hours). 
The lesions as well as the distribiiiion of the bacilli and cultures from blood and 
spleen were the same as in preceding case. 

A pig inoculated subcutaueously with 2 cubic centimetres of turbid dei)osit from a 
fermentation tube showed no signs of disease. 

Whether these bacilli can be implicated in the death of some cases of 
this outbreak in which swine-plague bacilli were not detected, these 
inoculations will not i)ermit us to decide. The bacilli at the date of 
inoculation had been cultivated for 10 months, and hence may have 
become attenuated in the meantime. 



At the end of 1890, Veterinarian E. O. Schroeder was directed by the 
chief of the Bureau to make some examinations of swine diseases iu 
the West with the object of still further determining the distribution of 
hog cholera and swine plague. 

Among the several herds examined only one deserves mention, be- 
cause positive bacteriological results were obtained. This herd was 
found about 1^ miles south of Chillicothe, Missouri, where greater or 
smaller losses from infectious swine diseases are said to occur each 
year. 

Cultures were made by Dr. Schroed er on agar, and these were care 
fully examined by the writer subsequently. The cultures from one 
animal contained only swine-plague bacteria, those from another only 
hog-cholera bacilli. This outcome again illustrates the caution which 



83 

imist be exercised in isolatiug the bacteria obtained from diseased ani- 
mals, so that the characters of two ditterent bacteria may not be 
confonnded and regarded as one, as has probably been done by Bill- 
ings in his investigations. No conclusions are drawn from the meager 
details below as to which bacteria may have been the predominating 
cause of the disease. They sim{)ly illustrate the wide diffusion and in- 
termingling of two pathogenic bacteria. 

The following brief synopsis has been condensed from Dr. Schroeder's 
notes of the post-mortem examination: 

No. 1. December 27, 1890. Dead several days. Animal had been opened by owner. 
Spleen greatly congested. Intestines could not be examined. Right lung almost 
completely hepatized. Epicarditis. Lymjih glands in general mucli cong(\sted. 

No. 2. January 2, 1891. Several foci of hepatization in lungs. Muco-purnlent con- 
dition of smaller air tubes. Spleen very large, dark, softened. I'etechia? in cortical 
portion of kidneys. Much ujucus in stomach. Feces in large intestine very dry, 
coated with mucus. Patches of byperaimia; no ulceration. 

No. 3. January 3. On pubic region a large open wound, with subjacent tissue very 
much tliickened by inllannuatory deposits. Spleen very large, dark, and friable. 
Slight exudative peritonitis. Congestion of fundus of stomach. Feces in large 
intestine exceedingly dry and covered, with mucus. Several inches below valve a 
blackisb, necrotic patcb, 1^ inches long and a half-inch wide (Foyer's patch ?). Mucosa 
congested in isolated patches. No other ulceration observed. Lungs hyperaimic. 
No hepatization. Heiiiorrliagic condition of auricles of heart. Petechias on epicar- 
dium of ventricles. 

No. 4. January 3. Black female, killed by a blow on head. Spleen as in No. 3. Di- 
gestive tract normal, with exception of patches of congestion in large intestine and 
what appear to be two small ulcers on ileo-cecal valve (enlarged mouths of glands ?)• 
Sliglit exudative peritonitis. Lungs free from hepatization. 

Bacteriological examination. From No. 1 no cultures made, owing to post-mortem 
changes. 

From No. 2 bits of the spleen placed in two agar tubes. On January 19 there were 
about 100 isolated and contluent colonies on the agar surface in one of the tubes. In 
the other no growth had appeared. These colonies were carefully examined and 
found to be swine-plague bacteria. Many of the colonies were dead, as the agar had 
dried out somewhat. Transferred to bouillon and other media, the diagnosis was 
conlirmed. These bacteria were, however, more or less attenuated as regards patho- 
genic effect. 

January 31. Two white rabbits of medium size inoculated, one snbcutaneously on 
one ear with a loop dipped into condensation water of an agar culture, the other under 
skin of abdomen in same manner. Both rabbits were very quiet for several days, the 
former with ear drooping and very much reddened. On the elcA'enth day it was 
chloroformed. The greater part of the inoculated ear blackish ; hard, like a board ; 
necrosed. A purulent inflammation extending from ear down ou the face and neck. 
Heart muscle pale and Habby. Much fat in the fibers. Fattj degeneration of con- 
voluted tubes in cortex of kidneys. Numerous granular casts in uriue. Spleen small 
and pale. Fatty condition of liver. 

The second rabbit was well at this time. When killed a small abscess in subcutis, 
with ecchymosis of contiguous abdominal muscles. No internal lesions. 

From No. 3 agar cultures had been made from spleen and liver. Both developed, 
and evidently contained the same bacteria. The liver culture contained a consider- 
able number of isolated colonies. From these gelatin plates were made. The vari- 
ous culture tests and the microscopic characters (size, motility, etc.), all iwinted to 
hog-cholera bacilli. Tho diagnosis was confirmed by the following inoculations: 



84 

One rabbit received iuto au ear vein oue-tifth cubic ceutiiueter bouillon culture 
derived from a colony on a gelatine plate. One rabbit received same dose of same 
culture under skin of flank. 

The first rabbit died within 48 hours. No local lesion. Spleen very large, dark, 
and firm. Liver fatty. Lungs slightly cedeniatous. In the spleen numerous bacteria, 
resembling hog-cholera bacilli in every way. Cultures confirmatory. 

The second rabbit died in 5 days. At the place of inoculation purulent infiltration 
of skin and subcutis with ecchymoses on periphery. Spleen large, dark, firm. Heart 
muscle fatty. Lungs cedeniatous and hypenemic along ventral border. In liver 
interlobular tissue broadened, pale, representing degeneration of periphery of acini. 
Cultures contain only hog cholera bacilli. 

From pig No. 4 au agar culture irom the spleen failed to develop. 

XI. 

An intermingling of hog cholera and swine plague was also observed 
in two outbreaks studied in 18S9, and very briefly referred to in the re- 
port of the Secretary of Agriculture for the same year (p. 75). These 
outbreaks are of importance, in so far as the hog-cholera bacilli obtained 
therefrom were somewhat moditied with reference to their biological 
and pathogenic properties. It was evident also that these hog-cholera 
bacilli were the predominating cause of the disease in many of the ani- 
mals exposed, and the full report is therefore reserved for another pub- 
lication. The investigations are here mentioned to illustrate once again 
the wide distribution and frequent intermingling of these two patho- 
genic bacteria. 



THE BACTEIIIA OF SWINE PLAGCE. 



MORPHOLOGICAL AND BIOLOOICAL CnAUACTERS. 

If a cover-gl;iss preparation from the spleen pulp of a rabbit, whicli 
has saccambed 16 to 20 hours after inocuhition, ba stained in alkaline 
methylene blue for a few minutes, and examined with a high ])ower 
either in water or after it has been permanently mounted in balsam, 
a very large number of swine-plague bacteria will usually be found 
among the cells of the spleen pulp. 

These bacteria at first give the impression of very minute flattened 
cocci in pairs, the individuals of each pair separated from each other 
by a small intervening space. (See Plate xi, Fig. 1.) A closer inspection, 
however, shows that each pair is in reality a single elongated body of 
which the two cocci are the stained extremities. The intervening space 
is the unstained connecting body, the borders of which are contin- 
uous with those of the stained extremities as indicated in the figure. 

The two end pieces have usually a lunar shape, the concavities turned 
toward each other. The depth of the concavity varies somewhat and 
may even be replaced by a straight line, in which case the end pieces 
have a hemispherical shape. 

It is highly probable that the bacteria as described above are in a 
state of division, the two stained extremities representing the two future 
cells, and the intervening space perhaps a common membrane without 
any contents. During this process the protoplasm retracts from the 
central portion of the rod and gathers at the two extremities. 

In stained cover-glass preparations these bacteria are not infre- 
quently found varying in length. This variation is mainly due to the 
variation in length of the middle unstained piece. Thus preparations 
of the same germ from some rabbits may show a very short middle piece 
so that the two concave borders of the comparatively large end pieces 
appear to touch each other on the lateral margins of the bacterium. In 
other preparations this middle piece may be from two to three times the 
size of each end piece. In a jn-eparation from the spleen of a rabbit 
inoculated with the German swine plague the middle piece was in many 
bacteria so long as to suggest involution or degenerate forms. It made 
the entire rod one and one-half to two times longer than the normal 
forms. In some of these bacteria one end piece had divided and the 
double germ resulting therefrom appeared like a long, feebly stained 

85 



86 

bacillus, in which there were iu both ends and in the middle of the rod 
the deeply stained round coccus-like bodies. In all the variations the 
stained extremities do not vary much in size. This is, therefore, an ad- 
• ditional reason why these extremities should be regarded as daughter 
cells in process of separation from one another. 

The foregoing description applies to bacteria taken directly from the 
dead animal and dried on cover glasses. In this dried condition after 
they have been stained and mounted in balsam they are about 1 j.i* 
long and 0.5 to 0.6 /li wide. Their ends are rounded oft* and in general 
their form is that of a somewhat elongated oval. Besides these aver- 
age forms there may be others, 1.8 // long and 0.7 to 0.8 /u broad. Di- 
mensions larger than these generally belongto forms evidently abnormal 
in development. In these the width generally remains the same as that 
of the shorter forms. 

While these bacteria in cover-glass preparations from pigs, inoculated 
rabbits, etc., are the same in appearance, the same bacteria in sections 
of tissues hardened in alcohol and stained in the same way do not cor- 
respond to the description just given. They are smaller than the 
smallest forms described above, and as a rule do not show distinctly 
the unstained middle piece. They appear under high powers as mi- 
nute uniformly stained oval bodies. It is evident that in the one case 
the drying process has a tendency to flatten objects out against the 
cover glass, while in the hardening process there is a tendency to 
shrinking, which is not counteracted in any way. Hence the different 
appearance may be due simply to the difference in the mode of jjrep- 
aration. 

The foregoing description applies to virulent v^arieties which cause 
death of the inoculated rabbit in 16 to 20 hours. In the various 
organs and the blood the inoculated bacteria are present in large num- 
bers. The more attenuated varieties do not produce death thus quickly. 
The rabbit dies in from 3 to 10 days. The bacteria have meanwhile 
become localized iu the peritoneal cavity or the pleural cavity, and 
produced an inflammatory exudate which contains immense numbers ot 
bacteria. These do not stain so well as those described, and rarely 
show the polar arrangement of the protoplasm distinctly. There is 
reason to suppose that many of these forms are already destroyed by 
the inflammatory process. 

In cultures the swine-plague bacteria are smaller than in the bodies 
of inoculated animals. Examined in water they appear so minute that 
jt is with difQculty that they are detected at all (Zeiss apochr. 2 milli- 
metres, compens. oc. 4). In general they answer well to the descrip- 
tion of micrococci, although they are not round but oval in form. On 
the border of the drop holding them in suspension the polar arrange- 
ment of the protoplasm is occasionally detected. 

Swine-plague bacteria are non-motile. This imi)ortant character 

* Micromilliuaetre or about oae twenty-five thousandth of an inch. 



87 

serves to distinguisli them at once from liogcbolera bacilli. In liquids 
an active Brownian motion is frequently seen which is so violent at 
times as to give the impression of spontaneous motion. They do not 
change their place, however, and this agitation is thus readily distin- 
guished from the very active flagellar movement of hog-cholera bacilli.' 
Again, flagella are easily demonstrated on the latter. Dr. Y. A. Moore 
has devoted much time in the laboratory to bring out flagella on swine- 
plague bacteria without success. This was of course to be expected. 
No sj)ores have been observed in any of the conditions under which 
they have been cultivated. They are destroyed in liquids by a tem- 
perature of 5SO C. (136.4° F.) in 7 minutes. Their rapid destruction 
by drying, disinfectants, etc., renders it highly probable that no spores 
are i>roduced. 

The question whether swine-plague bacteria should be called bacilli 
or micrococci is not an easy one to settle satisfactorily. In the tissues 
and very rarely in cultures they may appear as elongated rods, but only 
under abnormal conditions. Their usual form, both in cultures and in 
sections from tissues, is that of an oval, the longer diameter exceeding 
but slightly the shorter diameter. While we are inclined to call them 
micrococci as least misleading, usage seems to have followed the Koch 
school in calling them bacilli. In the present report they are simply 
denominated bacteria, and the matter of nomenclature is left open. 

Swine-plague bacteria are not so easily cultivated as hog-cholera 
bacilli. Besides refusing to multiply on certain media in which hog- 
cholera bacilli readily grow, their life in cultures is much shorter. 
In the following the chief characters of these bacteria in the various 
culture media are given somewhat in detail, since no one character 
is sufficiently peculiar, and all are necessary to positively recognize 
the species. 

The growth on nutrient gelatine is variable and therefore not reliable. 
The bacteria from outbreaks VII, VIII, and IX, as a rule, refused to 
multiply in gelatine. Occasionally colonies develop in roll cultures, but 
the growth is very feeble and retarded, and may be overlooked unless 
they are carefully watched for longer than a week. An increase of 
alkali seems to favor their growth. 

If we turn to the bacteria discovered in 1886 and 1887 perhaps the 
only biological difference observable is the more abundant growth of 
these varieties in nutrient gelatine. The deep colonies were from one- 
fourth to one-half millimetre in diameter; the surface colonies were 4 or 
5 times as large. The former appeared after some days with a pale mar- 
gin, the central portion being brownish, granular.* The failure to grow 
on gelatine can not be regarded as entirely due to the lower tempera- 
ture in which gelatine must be kept. It seems partly due to the nature 
of the medium, partly to the adaptability of the bacteria to be cultivated. 

* See p. 89 and Plate iv in the report of the Bureau of Animal Industry for 1886, 
and Plate xii, Fig. 3, of this report. 



88 

The same method being employed in the preparation of gelatine and 
agar, the fact that swine-plague bacteria will develop in an agar tube 
when a gelatine tube by its side inoculated in precisely the same 
manner fails to develop shows that some physical or chemical con- 
dition of the gelatine is at fault. The gelatine must be regarded as a 
drier medium than the agar, which dryness is not so favorable. An- 
other j)ossible explanation of the refusal of the more recently cultivated 
varieties to multiply in gelatine may be due in part to slight improve- 
ments and modifications In the preparation of nutrient gelatine and 
agar. On the whole gelatine should not be used in the investigation 
of swine plague. 

On nutrient agar prepared in the ordinary way with peptone bouillon 
and kept in the thermostat, multiplication goes on rapidly, so that in 
24 hours the deep colonies are one-eighth to one-fourth millimetre in 
diameter according to the proximity of the colonies to one another (see 
Plate xii, Figs. 1 and 2). The deep or submerged colonies appear 
roundish or lenticular, and when examined under a low power (about 
60 diameters) they are brownish, opaque, with margin and surface beset 
with small knobs, thus giving the disk a reticulated and the border 
an irregular wavy appearance. Some colonies do not present this 
appearance, but remain smooth on surface and margin. The surface 
colonies are glistening, slightly convex, whitish disks, barely trans- 
lucent. They are circular, with margin having no irregularities. 
Under a low power the central portion is brownish, granular, towards 
the margin becoming more homogenous and translucent and exhibit- 
ing usually very delicate radial striations. The deep colonies may 
attain a diameter of one-half to three-fourths millimetre; the surface 
colonies, when 1 centimetre apart, measure 4 to 5 millimetres in diameter. 
As in the casQ of other bacteria, the size of the colonies varies inversely 
as their number on the plate. 

A very characteristic feature of such plates is the strong, disagree- 
able, pungent odor which is emitted. This is best detected when the 
agar plates have been prepared in so-called double dishes, and these 
are quickly opened after they have been closed for 24 hours or less. 
When the growth is abundant this odor persists even after repeated 
exposure of the ])lates. 

On the inclined surface of nutrient agar in tubes, the growth may 
appear either in the form of isolated colonies or as a single grayish trans- 
lucent patch, depending on the number of bacteria rubbed upon the 
surface originally. (See Plate xn, Fig. 4.) The condensation water 
collected in the bottom is usually quite turbid within 24 hours. After 
two or more weeks it will be found that the growth in the water has 
assumed a viscid gelatinous consistency, so that it tends to come away 
in a mass when a platinum loop is introduced. This has been charac- 
teristic of all swine-plague germs thus far examined. 

Bouillon containing from one-fourth to 1 per cent, peptone becomes 



89 

uniformly but very faintly clouded within 24 hours. From some out- 
breaks tlie jjrowth may be at first flocculent or granular. The bacteria 
grow in clumps, leaving the liquid unclouded. This, however, is no 
permanent character, since cultures of succeeding generations after a 
time become uniformly clouded, i^ot infrequently a partial membrane 
or a ring growth on the glass at the surface of the liquid appears alter 
one or more weeks of quiet standing in a uniform temperature. In 
the bottom a deposit forms during this time which may become quite 
viscid. No marked changes in reaction occur in the cultures even after 
some weeks of multiplication. There seems, however, to be a slight 
tendency toward the production of an acid reaction in culture liquids 
originally alkaline. No fermentation of sugars accompanied by the 
liberation of gases takes place. In this particular these bacteria are 
distinguished from hog-cholera bacilli, which are able to cause fermen- 
tation of glucose with liberation of hydrogen and carbonic dioxide.* 

Milk inoculated undergoes no changes visible to the naked eye. The 
reaction becomes faintly acid. On the surface of boiled potato there 
is no appreciable multii>lication. I have once or twice observed a very 
faint whitish growth which may have been due to the culture material 
transferred. In general, however, swine-plague bacteria do not grow 
on potato. 

The temperature range for the multiplication of swine-plague bac- 
teria may b(^ placed between 65° and 108° F. The growth is very 
feeble between G~)'^ and 70° F., and most rapid and abundant be- 
tween 970 to 100° F. The nature of the culture media seems to have 
some efi'ect. If this is very favorable multii)lication may take place at 
a slightly lower temperature than when less favorable. 

Among the i^roperties of the group of swine-plague bacteria pointed 
out by German observers, and valuable as a means of diagnosis, is the 
capacity to form in culture liqui<ls indol (CsHtN) and phenol or car- 
bolic acid (CeHfiO). Both substances are also formed ordinarily during 
the decomposition of albumins, and hence are present in the intestinal 
tract. 

The method followed in testing for these substances is that sug- 
gested by Lewandowski,t which consists in distilling the culture liquid, 
say 250 cubic centimetres of ordinary peptone bouillon in which the 
bacteria have grown for 10 days, with 50 cubic centimetres of strong 
chlorhydric acid and testing the first portions of the distillate, for indol 
and phenol separately. For indol 2 cubic centimetres of a 25 per cent 
solution of sulphuric acid is added to 5 cubic centimetres of the distil- 
late, and then 2 to 3 drops of a 0.1 per cent solution of sodium nitrite. 
A red coloration indicates the presence of indol. A fine crystalline 
precipitate forming immediately, or soon after the addition of bromine 
water to the distillate, indicates the presence of phenoU 

• See foot-note, p. 81. 

t Deutsche med. Woclienschrift. 1890, S. 1186. 



90 

The metliod followed by tbe writer was j^ractically the same, except- 
ing that potassium iiitrite was used, the solution being prepared fresh 
each time. A preliminary trial having shown phenol in most cultures, 
' but only a trace of indol in one culture, a second test was made. 

Slightly alkaline bouillon containing 1 per cent peptone and one-half per cent salt 
was sterilized in flasks containing 200 cubic centimetres each, and inoculated May 
15, 1891, with swine-plague bacteria from the following sources : 

1. Outbreak VII. 

2. Outbreak VIII. 

3. Outbreak IX. 

4. German swine plague (virulent variety). 

These cultures were allowed to remain in the thermostat until June 8, at which 
time they were tested according to the method indicated. 

The culture from VII had an abuudant viscid growth on the surface attached to 
glass. Liquid turbid when shaken, faintly alkaline ; odor disagreeable and charac- 
teristic of swine-plague cultures. Slight precipitate of tribrompheuol ; no indol 
reaction. 

The culture from VIII had a thick membrane on the surface, somewhat viscid. 
Other characters as in preceding case. Phenol less abuudant. No indol. 

The culture from IX like that of VIII. Phenol very abundant. Very faint indol 
reaction. 

The culture of (irerman swine plague gave nearly as much precipitate of tribrom- 
pheuol crystals as the preceding, but no indol reaction. 

Various cultures of hog-cholera bacilli tested showed the presence of neither indol 
nor phenol. 

The reason why the indol reaction failed in our hands is not clear. 
It may be that as the culture grows older the phenol reaction increases 
while the indol reaction may disappear. It will be noted that phenol 
was detected in all four cultures, in the third in abundance. The crystals 
of tribrompheuol examined microscopically were identical in all four 
cases. It might also be mentioned that the second culture, inoculated 
with the least virulent swine-plague bacteria, contained the smallest 
quantity of phenol. 

RESISTANCE OF SWINE-PLAGUE BACTERIA TO DESTRUCTIVE AGENTS. 

Swine-plague bacteria possess less power to resist destructive agents 
than hog-cholera bacilli. Their life, even under what might be regarded 
as the most favorable conditions, is brief. In the laboratory cultures are 
liable to die out in 3 or 4 weeks, especially when evaporation is going 
on. In bouillon but 2 or 3 days old the large majority of bacteria are 
dead, for'if j)late cultures be made from the liquid only very few colo- 
nies appear where we would expect thousands. The resistance to dry- 
ing is feebler than that of hog-cholera bacilli. In the report for 1886, 
some experiments are reported which show that drops from a bouillon 
culture dried on cover glasses failed to infect fresh tubes on and after 3 
days. Shorter periods were not tried in this experiment. 

In another trial with peritoneal exudate from a rabbit containing im- 
mense numbers of swine-plague bacteria dried on cover glasses, bouillon 
tubes were infected up to the third day, but not thereafter. 



91 

In the report for 18S7-'88, p. 143, some adtlitionnl oxpernnents are 
given with swiiie plague bacteria from Iowa. Bacteria in bouillon cul- 
tures, dried for a period longer than 3(5 hours, were destroyed, while 
bacteria from agar cultures lived for « days. The difference is very 
likely due to the thickness of thedried film, which is much greater when 
material from agar cultures is employed, owing to the density of the 
growth. 

They are likewise more easily destroyed by disinfectants than are hog 
cholera bacilli. Ilence the extended experiments made in connection 
with our study of hog-cholera bacilli have made a repetition of such 
experiments with swine plague unne(;essary. We simply give the fol- 
lowing experiments with lime, since this disinfectant is cheap, efficient, 
and easily applied. 

April 18, 1H91. Five cubic centimetres of limewater is thorouslily mixorl with a 
loop of agar growth of swinc-plagne bacteria 1 day old from outbreak IX. Bonillon 
tubes; inoculated with a loop of this suspension after 45 minutes, 1, 2, 3, aud 6 hours, 
remain clear. 

This experiment was repeated with the modification that two hiopsof agar growth 
were mixed with the limewater aud bouillon tubes were inoculated immediately after 
making the mixture, and after 5, 10, 15, 20, 25, 30, 40, 50, aud 60 minutes. All but the 
first tube remained clear. 

The limewater in a third trial was diluted with two volumes of water, and therefore 
contained but 0.04 per cent of lime approximately. In this .series all but the tube, 
inoculated immediately after the bacteria were mixed with the limewater, remained 
clear. 

These experiments show that as weak a solution of limewater as 0.04 
per cent is sufficient to destroy swine-plague bacteria almost imme- 
diately. 

The rapidity with which swine-plague bacteria are destroyed by dry- 
ing aud other agencies made it very probable that their life in the su- 
perficial layers of the soil where they are deposited must be very brief. 
The following simple experiments place this supposition beyond doubt, 
for they show that rabbits can no longer be infected after the bacteria 
have been in the soil for a period of 8 to 10 days. 

March 7, 1888. A pot of sterilized soil was inoculated by pouring upon its surface 
50 cubic centimetres of a beef-infusion peptone culture which had been growing for 
24 hours at 9.5° F. The pot was kept iu the laboratory, covered with a disinfected 
bell jar. March 10 a rabbit was inoculated with one-fourth cubic centimetre of 
sterile beef infusion in which a little soil had been stirred up. The rabbit died iu 48 
hours with numerous polar-stained swine-plague bacteria in the internal organs. 
Ten and fourteen days respectively after the soil had been infected two other rabbits 
were inoculated from the same soil. Both remained well. 

March 29. A pot of soil was inoculated by pouring upon its surface 100 cubic centi- 
metres of a beef-infusion peptone culture 2 days old of swine-plague bacteria obtained 
through Prof. W. H. Welch from an outbreak studied by him in 1887 in Baltimore, 
Md. The pot was sunk into a larger pot filled with sterilized soil and the whole 
buried in the garden of the Department of Agriculture on a level with the soil. To 
test the virulence of the culture used to infect the soil a rabbit was inoculated in the 
ear with a lancet dipped into it. It died within 48 hours. Cover-glass preparations 
and cultures reveal the inoculated bacteria in the internal organs. Four days later, 



92 ^ 

a rabbit was inoculated from the soil as in the preceding experiment. The rabbit 
died within 2 days. No bacteria found on cover-glass preparations; cultures contain 
several kinds of bacteria. Swine- plague bacteria not detected. This case was there- 
fore doubtful. April 7, nine days after the infection of the soil, another rabbit was 
inoculated therefrom. This one remained well. 

Some experiments made iii 1886 indicated a rapid destruction of swiue- 
plague bacteria in sterilized water. In 1888 and 1889 Dr. V. A. Moore 
was charged to carry out another series of experiments to test this 
problem more thoroughly. 

In the first experiment a platinum loop rubbed over the surface growth of an agar 
culture 24 hours old was stirred up in 10 cubic centimetres sterilized Potomac water 
and placed in the laboratory. A second tube of water prepared in the same way was 
placed in the refrigerator (50°-r)r>o F.). 

From the first tube 1 cubic centimetre transferred to bouillon on the fifth day failed 
to infect it. From the second tube the same quantity failed to infect a bouillon tube 
on the seventh day. 

In a second series two tubes of water were infected, each with three loops of surface 
growth and three drops of condensation water from an agar culture. It will be 
noted that in this case some nutritive substances must have been transferred in the 
condensation water. Bouillon tubes were infected up to tlie thirty- fifth day fvota the 
water in the laboratory. From that in the refrigerator a successful inoculation was 
made on the nineteenth day, but it failed after 38, 41, and 44 days. 

A third series was tried. Each of two tubes was infected with three loops of growth 
from an agar culture 1 day old. From the one in the laboratory inoculation with 1 
cubic centimetre failed on the ninth day ; from the one in the refrigerator, after the 
twentieth day. 

Swine-plague bacteria in water containing no nourishment maj^ thus 
succumb in 7 to 10 days at ordinary temperatures (<!0O-70oF.). When 
some nutritive substances are present this period may be materially 
lengthened. In lower temperatures tlie bacteria seem to live somewhat 
longer. A comparison between the relative vitality of hog-cholera and 
swine-plague bacteria may be tabulated as follows : 



Destroyed by moist heat at 58° C 

Destroyed by dryiu" (from bouillon) 

Destroyed by dryiug (tVom anar) 

Destroyed in water 

Destroyed in soil 



Swine plague. 



7 minutes 

IJ to '2 days . . . 
After 6 days. . 
After 10 diiys. 
After 4 days . . 



Hog cholera. 



15 minntes. 
7 to 9 days. 
After 4 months. 
After 2 to 4 months. 
After 2 to 'i months. 



THE PATnOGEXIC ACTION OF SWINE-PLAGUE RACTERIi 

EFFECT ON SMALL ANIMALS. 

In order to uiulerstaud best the pathogenic action of swine-phigue 
bacteria a brief acconnt of the results of inocuhition into smaller ani- 
mals will be given before the disease in swine is discussed. These in- 
oculations being made with pure cultures the effects are exhibited in a 
clearer manner than in swine in which hog cholera is so frequently' an 
associated disease. 

The various inoculations into the smaller animals, such as mice, rab- 
bits, guinea-pigs, pigeons, and fowls, are briefly described in connection 
with the special outbreaks from which the l)a<;teria were obtaiiuid. In 
the present chapter ouly the general results will be brought togetiier 
and broadly outlined in their bearing on swine plague. 

If we take the inoculation of rabbits as a starting point we find that 
there are different degrees of virulence or pathogenic activity very 
clearly brought out. Thus the swine- plague bacteria obtained from out- 
breaks VIT and IX, and from Germany,* were of the maximum degree 
of virulence so far as rabbits are concerned, inasmuch as the latter 
died 16 to 20 hours after inoculation with very minute doses of culture 
material. The blood and the various organs contained often immense 
numbers of the inoculated bacteria, always exhibiting the very charac- 
teristic polar stain shown in Plate xi. Fig. 1. These bacteria were thus 
able to produce a rapidly fatal septica3mia. 

The bacteria from some of the other outbreaks (such as I, II, IV, V, 
and VIII) were not so virulent. The rabbits inoculated under the skin 
died from 40 hours to 7 days after inoculation. In many such cases 
the acute septicaemia was no longer present, but a peritonitis quite 
invariably appeared. In the more rapidly fatal cases this was hemor- 
rhagic; in the others a considerable amount of grayish, sometimes quite 
viscid, exudation had taken place. This covered the caecum, liver, and 
spleen with a thin pseudo-membrane, and was found to some extent 
between the coils of the large intestine. The exudate consisted of leu- 
cocytes, fibrin, and immense numbers of bacteria. The relative propor- 
tions of these elements varied according to the age of the disease, the 
leucocytes being most abundant in the advanced stages. The swine- 
plague bacteria were localized more or less in the peritoneal cavity. 
The spleen and liver and the blood contained very few. 

• For experimenta with cultures of the Germau awine plague see pp. 127-129. 

93 



94 

The course of the disease did not always correspond to this descrip- 
tion. In a small number of instances the subcutaneous inoculation was 
followed not by peritouitis but by pleuritisaud pericarditis. The exudate 
into these serous sacs was of the same nature as the peritoneal exudate 
in other cases. More rarely thepleuritis was accompanied by a genuine 
pneumonia of a croupous character. 

A third form of the inoculation disease is produced by very attenu- 
ated swine-plague bacteria. This attenuation may have been due to 
long: cultivation in the laboratory or else it may have taken place in na- 
ture. The rabbits inoculated subcutaneously may live several weeks. 
The place of inoculation becomes the starting point of a partly hemor- 
rhagic, partly purulent infiltration and thickening of the skin and 
subcutaneous connective tissue which may extend over the entire 
abdomen and thorax. The skin in places may become necrotic, dry, 
and hard. If the animal survives, which is not infrequently the case, 
the inflammation becomes circumscribed into an abscess which finally 
heals. In these cases internal changes such as peritonitis and pleuritis 
are absent. In some cases, however, a parenchymatous and fatty de- 
generation of the heart muscle and the kidneys is present. 

Such attenuated bacteria are still capable of producing all the vari- 
ous lesions ascribed to the more virulent varieties when injected directly 
into the circulation. This is very easily done by choosing a vein of the 
ear. After such injection we may produce a rapidly fatal septicsemia, or 
inflammation of the serous membranes, according to the quantity of 
virus injected and the relative virulence. The localization is the same 
as with subcutaneous inoculations. In rare cases even intravenous 
injections of small doses do not prove fatal, and tlien we may observe 
further localization of the virus in the joints of the extremities, chiefly 
the lower, or even in the subcutaneous and intermuscular connective 
tissue in diflerent parts of the body. Such localizations were in a state 
of suppuration when' they came to our notice. 

It might be maintained that the attenuated swine-plague bacteria, 
such as those from outbreaks VIII and X, were specifically diflferent 
from the very virulent varieties obtained from outbreaks VII and IX, 
owing to the differences in the rabbit disease produced by them. We 
have, however, carried out experiments which dispose of this possible 
objection. By making rabbits more insusceptible to the virus of swine 
plague by vaccination we have been able to vary the. disease produced 
by virulent varieties so as to produce nearly all the forms caused by 
attenuated varieties. For example, those bacteria (IX) which produce 
a rapidly fatal septiciemia have, in vaccinated rabbits, produced a pro- 
longed disease characterized in some cases only by local reaction at the 
point of inoculation and recovery, in others by peritonitis or pleuritis 
and pneumonia. The two following cases are interesting illustrations: 

Rabbit No. 19 received into an ear vein about 13 cubic centimetres 
of bouillon culture of swine-plague bacteria, sterilized at 58° C, in five 



95 

doses at periods '6 to 4 days apart. On May 26, 1801, 5 days after the 
last injection, it was inoculated subcutaneously with one five-hundredth 
cubic centimetre of a bouiHon culture of livinj; s\vine-})laj;ue bacteria. 
While a check rabbit (not treated) died within 20 liours after inocula- 
tion, this rabbit died at noon June 2, i. e., 7 days after inoculation. The 
skin and subcutis at the i)oint of inoculation extensively thickened by 
purulent infiltration. Double exudative pleuritis and pericarditis icith 
large pneumonic regions in both lungs in which the hepatization had ad- 
vanced to the gray stage. Bits of this lung tissue examined fresh were 
made up chielly of leucoc^'tes. Swine-plague bacteria in exudate and 
spleen. 

Two other rabbits treated with one additional injection of sterilized 
bouillon cultures had considerable local swelling after the test inocula- 
tion, but both recovered. 

Another set of four rabbits were treated with sterilized agar cultures 
suspended in bouillon.* Only one succumbed to the test inoculation 
in 6 days, while a fresh rabbit succumbed to the same inoculation (one 
five-hundredth cubic centimetre bouillon culture of swine-plague bac- 
teria from outbreak IX) in 20 hours. The lesions in the vaccinated 
rabbit were extensive local subcutaneous infiltration, double purulent 
pleuritis and pericarditis, and congestion of both lungs. 

The numerous bacteria in the exudate were not attenuated, for a rab- 
bit inoculated with a particle from the pleural cavity died within 20 
hours. 

An exceedingly interesting element in these results is the tendency 
of the swine-i)lague bacteria towards the production of disease of the lungs 
and serous membranes in thes(^ treated rabbits. The vaccination they have 
undergone has placed them nearer the })ig as regards insusceptibility. 

A great variety of pathological conditions is thus produced by differ- 
ent degrees of virulence of the same species of bacteria, the significance 
of which will be appreciated when we come to the disease in swine. If 
we would arrange the various lesions according to their fatality, the sep- 
ticaemia or multiplication of bacteria in the blood stands first. Next 
come peritonitis, i)leuritis, and pericarditis with or without pneumonia, 
and lastly joint disease. 

The relative virulence of swine-plague bacteria from different sources 
thus demonstrated on rabbits has its counterjtart in the relative viru- 
lence of the same bacteria with reference to different species of animals* 
The susceptibility of the animals used Is greatest in rabbits and gray 
mice, and diminishes in guinea-pigs, pigeons, and fowls in the order 
given. 

In guinea pigs the lesions produced by subcutaneous inoculation 
present the various forms which we have seen characteristic of rabbits. 
There is this dilference, however, that the more attenuated varieties 
are likely to have no effect on guinea-pigs beyond a slight local reaction. 

* See p. 148 for details. 



96 

In pigeons and fowls the inoculation disease is a septicaemia, produced, 
however, only by the most virulent varieties of swine-plague bacteria. 
Attenuated varieties have no eflect. 

We have seen that the bacteria from outbreaks VII and IX, and 
from Germany, all produce a rapidly fatal septicaemia in rabbits, and in 
so far no difference in their ])athogenic power is manifest. But the 
guinea-pig inoculations make a discrimination in showing that the bac- 
teria from VII are less virulent than those from IX. Inoculation with 
the latter, even in very minute doses (see p. 7G), produces a rapidly 
fatal septicaemia, and heuce the effect on rabbits and guinea-pigs is 
alike. Inoculation with cultures from VII are on the other hand fatal 
to guinea pigs only after some days, and the localizations are uncertain 
just as with attenuated swine-plague bacteria in rabbits. The inocula- 
tion of pigeons also shows this difference. Bacteria from VII are fatal 
only when the injections are made slightly into the muscular tissue. 
The bacteria from IX are fatal in 24 hours, even when a very miuute 
quantity of the culture is placed under the skin. 

In case of fowls neither variety of bacteria is fatal when introduced 
under the skin. When, however, the needle punctures the pectoral 
muscle the bacteria IX prove fatal in 36 to 48 hours. With pigeons the 
case is similar. Bacteria which fail to produce any effect when i)laced 
under the skin may still prove fatal when injected into the muscular 
tissue. 

A further discrimination is possible in still more refractory animals, 
such as swine. It has been shown in the preceding pages that swine- 
plague bacteria from outbreak IX are the most virulent which haveyet 
been encountered. One of the cultures of the German swine plague is 
still more virulent, since it proves fatal to swine after subcutaneous in- 
oculation, while the American variety usually fails. 

The nature of the pathogenic activity of swine-plague bacteria is to 
a certain extent cleared uj) by these experimental inoculations. When 
they are capable of multiplying in the blood they produce speedy death, 
probably by the development of some poison and by a modification of 
the blood. When multiplication in the blood does not take place, the 
large serous cavities still permit their growth on the lining membranes. 
The irritation thus set up induces a fibrinous and cellular exudation, 
which later on becomes completely cellular. The means by which the 
bacteria are destroyed in these cavities when recovery ensues is not 
known. Phagocytosis probably plays an important role here, for I have 
frequently seen large numbers of bacteria imbedded in the protoplasm 
of the leucocytes. The pleural cavity is less frequently involved. This 
may, however, be due in jpart to the fact that in most cases the inocula- 
tions were made in the region of the abdomen or the thigh. 

The relative virulence of the varieties investigated thus varies con- 
siderably. Of those studied in detail recently the highest degree of 
virulence would belong to one form of the German swine plague. The 
others may be arranged in the following order : IX, VII, VIII and X. 



97 

THE DISEASE IN SWINE AS PRODUCED BY THE INOCULATION OF 

CULTURES. 

In order to determine the efifect of pnre cnltures swine were inocu- 
lated under the sl^in, into the veins, into the hmgs, and into the abdom- 
inal cavity. They were also fed with cultures and with the viscera 
of small animals which had succumbed to inoculation. The details of 
these experiments have been given under the dilVerent outbreaks, and 
it now simply remains to bring the facts together. 

It is at once apparent that any method of inoculation whatever can 
merely approximate the conditions prevailing in outbreaks of disease. 
The body receives in the one case a large number of bacteria at one 
time, while in the natural disease animals are being constantly infected 
by small quantities. A single small dose frequently repeated — and this 
is what actually takes place in an infected herd — may produce far more 
serious results than a single large dose. Again, the repetition of small 
doses may produce a disease quite dittcrent in character from that pro- 
duced by a single large dose of the virus; finally, the ways in which 
bacteria enter the body, in the natural disease, vary greatly, and differ 
in most respects from the ways in which they are introduced experi- 
mentally. 

These and many more considerations which need not be discussed here, 
serve to show that with inoculations into swine we may attempt but 
imperfectly two objects, first, to demonstrate that the bacteria under in- 
vestigation do actually produce disease, and, second, that they may have 
a predilection for certain organs and tissues of the body where certain 
kinds of lesions are produced. 

The inoculations in swine produce practically the same lesions as 
those which follow the inoculations of the smaller animals. Here we 
observe variations in the localization of the injected bacteria similar to 
those produced by attenuated cultures in rabbits and guinea-pigs. 

Feeding cultures and viscera of inoculated rabbits has thus far 
proved negative. 

Subcutaneous inoculation has in most cases proved negative except- 
ing with bacteria from outbreaks I, II, and IX. One variety of the 
German swine-plague bacteria i)roved in most cases fatal after subcu- 
taneous inoculation.* This, as has been stated before, gives them a 
higher potency than any American variety thus far encountered. 

Injection of cultures into the circulation is usually fatal when viru- 
lent varieties are employed. These lesions depend upon the time elaps- 
ing between inoculation and death, which in turn varies according to the 
virulence and the quantity of culture liquid injected. t 

When the animals die within one or two days the visible changes are 
confined to the blood, and in some cases extend to the peritoneum and 

* See p. 93, 

t A full account of these inoculations is given on pages 71-75. 
16U 7 



98 

pleura, wliicli are inflamed and covered witli more or less exudation. 
If tlie animals live longer these changes become more accentuated, and 
in several cases portions of the lungs become hepatized. This hepatiza- 
tion may be looked upon as secondary to the pleuritis, as in case of the 
rabbits having similar lesions. In two cases the bacteria became local- 
ized in various joints of the body, where necrosis of bones and suppura- 
tion took place. Intermuscular collections of pus were also observed. 
The duration of the disease in these cases was several weeks or longer. 
Other organs, excepting the pericardium, in one of these animals, were 
not directly affected. 

When the bacteria are injected directly into the lung tissue through 
the chest wall, death may follow within 16 to 24 hours, or life may be 
prolonged and severe pleuritis and pericarditis associated with hepati- 
zation of the lung tissue, may appear. Thus in pig 275 (see Plate vi) 
though the injection was made into the right lung, as a result the major 
l)ortion of the left lung also was involved in pneumonia. 

In a few experimental cases the intestines were involved, In one 
case, as a result of the peritonitis following an intra-abdominal injec- 
tion, the walls of the small intestine were swollen, inflamed, and a 
copious, friable, yellowish exudate had formed on the deeply inflamed 
mucosa. In another case all Peyer's patches in the small intestine were 
swollen, very hj'pertemic, and in part hemorrhagic. Intense hyperuMuia 
of the mucosa of the stomach has been observed in several cases, both 
after intravenous and intrathoracic inoculation, 

SAVINE PLAGUE AS OBSERVED IN EPIZOOTICS, 

The variety of lesions produced by the inoculation of swine-plague 
bacteria is by no means so great as that observed in nature. While 
there are outbreaks in which considerable uniformity is observed, there 
are others in which each animal is a surprise to the pathologist. In 
general it may be stated that the lungs and the digestive tract are the 
chief seats of the disease, though other organs, notably the lymphatic 
glands, are secondarily involved. The disease is localized in the lungs 
and the digestive tract most likely because the bacteiia gain enti'anco 
tlirongh the respiratory and digestive passages. 

The lungs have been found diseased in nearly every outbreak which 
has been investigated. In some (notably IV, YII, and VIII) the lung 
disease is the predominating aftection and the direct cause of death. 
In IX pneumonia was absent in some cases, but pleuritis and interlob- 
ular (edema were generally present. The localization of the disease in 
certain lobes of the lungs is quite constant. The ventral lobes are first 
attacked, next come the cephalic and azygos, and lastly the principal 
lobes. This movement of the disease seems to depend on gravity, inas- 
much as the diseased is marked off" from the healthy portion by a nearly 
horizontal line. In other words, the most dependent portions of the 



99 

lungs are the ones affected first, and as the disease progresses upwards 
only a small portion of the principal lobe, directl}' under the back of the 
animal, remains pervious, provided the life of the animal is maintained 
up to this point. This localization of the disease is indicated on Plates 
I and II, in connection with which a description of these drawings will 
be found. A similar distribution of disease I have observed in cases of 
bovine pneumonia due to bacteria and to actinomyces, and in isolated 
cases of pneunjonia in swine, the cause of which I was unable to trace 
at the time. In fact, in nearly all cases of pneumonia in swine, except- 
ing a few which were either caused by lung worms or due to embolism, 
the disease involved the regions described and indicated on the plates 
by shading. In the exceptions the pneumonia involved portions of the 
principal lobes not contiguous to the ventrals. 

Pathologists have delined two kinds of pneumonia, croupous and 
catarrhal pneumonia, or bronchopneumonia. In the former the vesic- 
ular portion of the lung substance is chiefly ail'ected ; in broncho- 
pneumonia the smaller bronchioles are said to be primarily affected and 
the vesi(;ular portion or alveoli secondarily. In croupous pneumonia, 
there is, following the stage of congestion, an emigration of red blood 
corpuscles, some leucocytes, and an exudate of fibrin into the alveoli. 
These elements are firmly matted together by the coagulating fibrin, 
making the diseased lung firm to the touch. In broncho-pneumonia 
the catarrhal condition of the smaller air tubes makes them impervious 
to air. The lung tissue which they supply is gradually emptied of air 
and assumes the appearance of red flesh, owing to the collapse of the 
walls of the alveoli and the distended condition of the capillary net- 
work. Subsequently the infiamuiation extends into the alveoli, which 
then become distended with cellular masses. 

The definitions of pathology do not always apply to classification of 
lesions from the standpoint of etiology or causatiou. A definition from 
an anatomical standpoint refers to a condition. The same bacteria may 
under different circumstances produce a variety of conditions. Another 
difficulty meets us in attempting to describe the lesions due to bacteria 
in animal organisms. The definitions have had their origin in human 
diseases and are not always applicable to animal diseases. Moreover 
there is a difference between different species of animals. Anyone who 
has experimented with different animals knows that they do not react 
exactly alike after inoculation with the same bacteria. There seem to 
be certain peculiarities belonging to each species which have not yet 
been clearly formulated by comparative pathology. They may be due 
to diCterences in anatomical structure or to physiological peculiarities. 

It is furthermore evident that the nature of the lung disease will de- 
pend more or less upon the mode of entrance of the virus. If it can 
enter only by way of the air tubes it will ap[)ear periia])s as a broncho- 
pneumonia. If it can enter the lung tissue through the circulation we 
may have more or less scattered centers of hepatization (embolic pneu- 



100 

monia). If it can enter by way of tlie pleura, the virus will creep alonji^ 
the interlobular and peribronchial tissue before it invades the paren- 
chyma proper. 

In natural infection the swine-plague bacteria enter the lung tissue 
chiefly bj'^ way of the air tubes. At the same time it is not improbable 
that occasionally they may enter the serous cavities first, i. e., invade 
the pleural cavities and thence the lungs. This i^robability is shown 
by our inoculations in which intravenous injections produced exudativa 
pleuritis, and pneumonia of the most dependent portions of the lungs 
covered by the pleural exudate. It is not improbable that even in the 
natural disease the bacteria which have gained access to a portion of 
the lung tissue by way of the air tubes reach the pleura covering this 
portion, and may then by this route invade other portions of the lungs. 
It may be that in this way a pneumonia originally single may become 
double. I have also observed not infrequently that the first pneumonic 
infiltration of the principal lobe was at the points of contact with the 
diseased ventral lobe, and that the resting of a lobe against an inflamed 
serous surface, such as the pericardium, caused a pneumonic infiltration 
at the i^oint of contact. 

These facts go far to show that swine -plague bacteria may invade 
the lungs both from the air tubes and the pleural cavities. I am not 
inclined to believe that pneumonia is produced to any extent by swine- 
plague bacteria acting as emboli in the circulation, because they are 
rarely found in the blood. Comparative inoculation experiments in rab- 
bits show that the chief indication of attenuation is inability to multi- 
ply in the blood. This probably holds with equal force in swine whose 
power of resistance is so much greater than that of rabbits. 

We may, therefore, expect to find the character and seat of the lung 
lesions somewhat varia ble— and this is actually the case. It would be 
difiicult to find two lungs exactly alike so far as gross appearances go. 
This to be sure may be due largely to the fact that animals die in dif- 
ferent stages of the disease. Yet there are difl'erences evidently not 
dependent on this fact which must be left for special pathological in- 
vestigation. 

After these preliminary remarks we turn to a brief description of a 
swine-plague lung. In general the cephalic (anterior) half is hepatized, 
of a dark-red or grayish-red color, firm to the touch. The pleura is more 
or less thickened and opaque, and covered with easilj^ removable friable 
false membranes. In the more recently aftectod regions a faint but 
quite regular delicate mottling with yellow is observed to shine through 
the pleura when not thickened. These minute, hazy, yellowish dots 
usually occur in groups of four. Occasionally whitish or yellowish 
jiatches varying much in size are seen perhaps more frequently in the 
ventral lobes. These correspond to homogeneous dead masses of lung 
tissue. 

When such lungs are cut into, the section presents much the same 



10! 

appofiraiieo, both as roc^ards color, inottliii.n', otc, as when viewed from 
the surface, excepting' that the (Uitails are less distinct. In some cases 
in the most recently invaded territories in the principallobe and nearer 
the dorsum in the other lobes, the dark or f>rayish-red cut surface shows 
grayish lines usually arranged in curves and circles. These, so far as I 
could determine, represent the cut outlines of the interlobular and peri- 
bronchial tissue infiltrated with cells. It has already been stated that 
these lines may represent the ])aths along^ which the swine-plague bac- 
teria invade the lungs from the])leural surface. 

The cut ends of the bronchi of the ventral lobes are frequently oc- 
cluded with thick, whitish pus; in the other lobes a reddish froth is 
usually present. Rarely they also contain thick glairy mucus in which 
particles of dry i)us and lung worms are imbedded. The contents of 
the air tubes in the ventral lobes may have been derived from the over- 
distended alveoli, or else a broncho-pneumonia, may have preceded the 
swine-plague pneumonia. 

In microscopic sections of diseased lung tissue the alveoli and small- 
est air tubes are found distended with cell masses consisting chiefly of 
leucocytes. I have seen very little librin and very few red corpuscles in 
the alveoli, even in cases in which the disease was quite recent. It may 
be that the stage represented in ordinary croupous pneumonia by the 
presence of fibrin in connection with the cellular elements is very brief, 
and that it is speedily replaced by large numbers of leucocytes. The 
large predominance of these elements in some portions of the lungs, as 
well as beginning fatty degeneration, is probably the cause of the reg- 
ular mottling of the lungs, as seen from the surface and above referred 
to. (See Plate ix. Fig. 2.) The little yellowish hazy dots represent 
the filled and distended alveoli surrounded by the hyperaimic walls. 

The necrotic and caseous changes so frequent in swine plague deserve 
brief attention. The caseous changes were particularly noteworthy in 
outbreak IV (Plates vii and viii, Fig. 1) and necrotic foci especially 
abundant in outbreak VII. (See Plate V.) The latter are usually 
quite small and disseminated in large numbers over the diseased lobes. 
The former represent larger masses from a marble to a horse-chestnut 
in size. There is need for a distinction between these two forms of 
necrosis, as I regard them as due to different processes. 

The necrotic masses represent tissue which has been destroyed by 
the rapid multiplication of swine-plague bacteria in particular locali- 
ties. Hence they are found in all stages of the pneumonia. The large 
caseous masses may be considered as the result of a slow death of 
larger territories of lung tissue, due primarily to the gradual overdis- 
tension of the tissue by leucocytes, and hence the gradual cutting oft" 
of the blood supply. One is a rapid death due directly to highly viru- 
lent bacteria, the other a slow death, or in other words a kind of dry sup- 
puration in the later stages of the pneumonia, characteristic of the pig, 
and due indirectly to the irritation of ijerhaps more attenuated races 
of bacteria. 



102 

It has already been remarked that different species of animals react 
Homewhat differently to inflammatory agents, and the tendency towards 
caseation in the lungs of swine is, I think, an illustration of the kind of 
reaction manifested by swine .as a species. When irritating substances 
or cultures of bacteria are injected under the skin of pigs, there is a 
tendency to the formation of a rather firm tumor-like swelling. This 
tumor at first consists of a rather tough, yellowish -white mass, and 
only after a time softens in the center into a thick, semi-liquid pus re- 
sembling flour paste. This tendency to a firm, dry infiltration of pus is 
likewise observed in the sometimes quite extensive button-like necroses 
or " ulcers" in the large intestine. The same may be said of the large 
homogeneous cheesy masses into which the diseased lung tissue is con- 
verted after a time. (See Plate vii.) 

It is not to be understood from the preceding that the pneumonia 
spreads from a single lobe, such as the ventral, in all or most cases. 
The case on page GD (No. 385) is a signal illustration of the contrary. In 
this every lobe contained some necrotic foci which were evidently due 
to a deposit of swine-plague bacteria in these separate localities, and 
which had not yet coalesced by an extension of the disease when the 
animal succumbed. 

The inflammation of the pleura frequently extends to the pericardium. 
(See Plate x.) This membrane is opaque, thickened, and its vessels 
distended. It may be glued to the contiguous lobes of the lungs and 
covered with exudate. Less frequently it is adherent to the surface of 
the heart, which is then covered by a false membrane, smooth or 
roughened, extending upon the large vessels emerging at its base. 

DISEASE OF THE DIGESTIVE TRACT IN SWINE PLAGUE. 

In order to elucidate this important subject we may briefly refer first 
to the results of inoculation, second to those cases of natural swine 
plague from which hog-cholera bacteria can be safely excluded. 

In a considerable proportion of those animals which were inoculated 
with swine-plague cultures a severe catarrhal inflammation of the lin- 
ing membrane of the stomach was produced. The hypera'-mia was 
very intense, bordeiing on hemorrhage. Again, in another case the ex- 
tension of the peritonitis, produced by intra-abdominal inoculation, 
along the mesentery caused a severe inflammation with exudation on the 
mucosa of the small intestine. In one case all Peyer's patches of the 
small intestine were in a hyperremic, partly hemorrhagic condition. 

In outbreak VIII there was observed in o out of 5 cases more or less 
extensive hyperemia of the mucosa of the large intestine bordering on 
a hemorrhagic condition. In the case (^o. 385) caused by infection 
from outbreak IX, the inflammatory condition of the large intestine 
was a prominent lesion. In these cases hog-cholera bacilli may be ex- 
cluded with reasonable certainty. In the earlier cases of outbreak lY 
a peculiar croupous exudation appeared, which I have considered and 



103 

still rej]rar(l as the effect of swine-phis'iio bacteria in the largo intestine. 
(See Plate viii, Fig. 2.) Ol' this lesion more or less has been said on page 
24, iu connection with a brief review of the ontbreak. It will be remem- 
bered that in this epizocitic hog-cholera bacilli were fonnd in the later 
cases, while swine-i)lagne bacteria were present in a large proportion of 
both earlier and later cases. The croupons inflammation in this out- 
break differed markedly from the necrotic and diphtheritic inflammation 
caused by hogcholera bacilli. At the same time we must regard it as 
unsat isfactory in the present state of knowledge to reason irom the 
pathology of swine disease to its etiology. 

In the remaining outbreaks two classes appear, those in which both 
swine plague and hog-cholera bacilli were readily detected (II, V, VII), 
and those in which hog-cholera bacilli were not found, or in which their 
relation to the disease was highly doubtful (I, VI, IX). In most of 
these outbreaks the intestines w'ere diseased, and the lesions resem- 
bled in general those found in hog-cholera epizootics. While there 
can be no reasonable hesitation iu attributing the intestinal lesions 
largely to hog-cholera bacilli when they are detected, it is diflicnlt to 
understand those cases in which hog-cholera bacilli are not found, or in 
which such attenuated forms are met with occasionally, the power of 
which to cause disease is highly questionable. 

It is reasonable to assume, at least until more knowledge is at hand, 
that, even in those cases in which hog^cholera bacilli are not detected 
in the internal organs and yet extensive necrosis and ulceration of the 
large intestine is present, these lesions are due to hog-cholera bacilli or 
bacteria not yet recognized* The difficulty of examining the intestines 
for pathogenic bacteria and the amount of labor involved is very great, 
and hence for want of time and sufflcient assistance this part of the 
work has been set aside in these investigations and the attention cen- 
tered on the lungs and the other internal organs. It is apparent that 
even if certain bacteria are found in the contents of the digestive tract 
their relation to disease processes going on there is by no means i)roved, 
since the intestines contain a large variety of bacteria at all times. It 
is necessary to demonstrate that with pure cultures of §uch bacteria the 
same, or a very similar intestinal disease, can be produced. While this 
demonstration has frequently been made by us with virulent hog-cholera 
bacilli, which are also quite invariably present in the sijleen, such dem- 
onstrations fail with swine-plague bacteria and with very attenuated 
hog-cholera bacilli, and we are at a loss to determine how much disease- 
producing power to attribute to them. 

The production of intestinal disease by swine-plague bacteria may be 
supposed to go on as follows: The bacteria first attack the lung tissue 
and there produce more or less hepatization. The blood finds its path 
through the lungs partly obstructed. This reacts on the blood in the 
right side of the heart and the venous blood entering it. Hence there 
may be more or less stasis of blood in the portal circulation which in 
turn impairs the digestive functions of the stomach. The swine-plague 



104 

bacteria in the lungs in the later stages of the pneumonia may be 
coughed up in the contents of the bronchial tubes, swallowed and passed 
through the impaired stomach unharmed into the intestines. The stagna- 
tion of feces in the large intestine furnishes the bacteria an opportunity 
to cause inflammation of the mucous membrane and exudation. The 
tendency of swine-plague bacteria to cause fibrinous inflammatory de- 
posits on serous membranes may serve to explain such action on mucous 
membranes. 

If we continue to follow the results of such jiossible localization we 
must assume that in the diseased intestine a considerable multiplication 
of swine-plague bacteria takes place, which, discharged with the feces, 
put into the surroundings of the swine a large number of pathogenic bac- 
teria. These swallowed by healthy pigs may lead directly to intestinal 
disease without any necessarily extensive lung lesions. The virus thus 
multiplied by the multiplication of cases will produce a more and more 
virulent epizootic in which intestinal lesions may predominate. While 
there is no proof that these phenomena actually take place, all the facts 
observed in an outbreak readily accord with such a hypothesis. 

The mingling of two diseases, hog cholera and swine plague,* makes 
it necessary to compare briefly the pathogenic power of the bacteria 
causing these diseases. This mingling has greatly complicated our 
understanding of the extent and the kind of lesions attributable to each 
bacterium. Thus, in hog cholera, the chief force of the disease is spent 
upon the digestive tract. The lungs are frequently involved in collapse 
and broncho-pneumonia of limited extent, but collapse seems to be not 
uncommon in apparently healthy pigs, and broncho-pneumonia may be 
conceived of as developing from collapse without the necessary interven- 
tion of disease germs. Again, the presence of lung worms may account 
for much of the localized bronchitis and hepatization. It is easy to 
understand that hog-cholera bacilli accidentally present in the blood in 
disease may pass through a healthy lung without injury, while lungs 
affected with collapse and lesions due to lung worms may offer a favor- 
able opportunity for the lodgment of emboli containing bacilli. The 
disease process thus starting up may be continued by sputum bacteria 
(resembling or identical with swine plague). It becomes difficult there- 
fore to determine whether hog-cholera bacilli have any specific effect 
on the lungs. 

In swine-plague the exact reverse is true. The predilection of swine- 
plague bacteria for the lungs is a demonstrated fact even with small 
experimental animals. Their exact eflect on the mucous membranes of 
the cascum is not easily determinable owing to the frequent association 
with hog-cholera lesions. That they produce a diffuse intense inflam- 
mation, associated at times with fibrinous exudation, will not, I think, 
be denied in view of the facts brought out in the experimental part of 
this report. 



* See also p. 138 for some practical observations on this subject. 



105 



We have thus in hog* cholera primary disease of the intestines with 
perhaps secondary localizations in tlie hinij;s; in swine phigne primary 
disease of the lungs with secondary infection of the intestines. 

The pathological action of these two kinds of bacteria can not be for- 
mulated with any precision without extended investigations directed to 
that subject alone. Meanwhile a few broad facts can be deduced from 
the inoculation experiments. Hog-cholera bacilli multiply in clumps 
in the capillaries of the j)areuchyma of the various organs, where they 
primarily obstruct the circulation, and thus produce necrosis of tissue 
in their immediate vicinity. When this takes place in the follicular 
apparatus of the intestine (in rabbits) necrosis of portions of the mucous 
membrane, followed by ulceration, may ensue. They do not produce 
fibrinous and cellular exudation on serous membranes, aiul probably do 
not multiply on these membranes. Secondarily, they produce paren- 
chymatous degeneration of the liver, kidneys, and heart-muscle, which 
degeneration may be due to the toxic bodies formed by them. 

Swine-plague bacteria, on the other hand, seem to multiply diffusely 
and abundantly wherever such multiplication takes place. When in 
the blood death is exceedingly rapid ; when in the large serous cavities, 
exudates are quickly produced and death may ensue in from 3 to 7 days; 
when under the skin necrosis and suppuration take place. 

The following table gives brietly the important differences observed 
between hog-cholera and swine-plague bacteria. Those features com- 
mon to both are omitted : 



SWlNE-PLAGUE BACTERIA. 

MorplwlogicaJ. 

1. About 1/i loug aucl 0.5 toO.f)// wide iu 

(cover-glass preparations niouutod 
in balsam). 

2. They show the so-called polar staiu 

iu certain conditions. 

3. Non-motile. 

Biological. 

4. Growth in bouillon feeble. 

5. Growth on gelatine feeble or absent. 

6. Growth on potato fails. 

7. Tends to produce acid reaction of cul- 

ture liquid. 

8. Produces no fermentation of glucose. 

9. Produces phenol and indol (?). 

10. Rapidly destroyed iu water, in soil, 
by drying.* 



HOG-CnOLEUA BACILLI. 

Morphological. 

1. About 1.2 to 1.5 /< long and O.G f.i 

wide. 

2. No characteristic polar stain, llie 

central part of rod frequently less 
stained than periphery. 

3. Motile (possess llagella). 

Biological. 

4. In bouillon moderate. 

5. On gelatine more vigorous than swine 

plague. 

6. On potato usually abundant. 

7. Tends to produce alkaline reaction. 

8. Causes fermentation of glucose with 

production of CO.2 and H. 

9. Produces neither phenol nor indol. 
10. Quite resistant to the same agents.* 



* See page 92 for table. 



106 



Pathogenic. 

11. Multiplies diffusely iu blood or on 

serous membraues. 

12. Produces septicix^mia ; fibrinous and 

cellular inflammation of serous 
membranes and pneumonia in small 
animals. 



13. Most virulent varieties are fatal to 
mice, rabbits, yuiuea-pigs, and pi- 
geons in very minute doses.* Death 
in 16 to 20 hours. 



Pathogenic. 

11. Multiplies In blood vessels in clumps. 

12. Does not produce inflammation of 

serous membranes. Produces pa- 
renchymatous degeneration of vital 
organs. Necroses in liver. More 
attenuated varieties cause infiltra- 
tion and ulceration of Peyer's 
patches and infiltration of lymph 
glands. 

13. Most virulent varieties are fatal to 

mice, rabbits, and guinea-pigs in 
minute doses." Death in 5 to 8 
days. 



In view of the mingling of these two diseases can we by inoculation 
of both bacteria at the same time gain any information as to their rela- 
tive activity? If both kinds of bacteria were of unchanging virulence 
this might be done, but we may have in natural outbreaks attenuated 
swine plague associated with virulent hog-cholera bacteria and the re- 
verse. Or one kind of bacteria may invade the animal after the other 
has spent its energy. The variety of combinations which may occur in 
nature is too great to be imitated by experiment. 

It was, nevertheless, desirable to see what effect the inoculation of 
mixed cultures might have. Hence the following experiment was tried, 
the result of which, though very important, is not conclusive. 

May 12, 1891. Cultures of swine plague from outbreak IX and of hog cholera. from 
a Virginia epizootic, both the most virulent in the laboratory, were chosen. From 
the growth on an agar culture of these swine-plague bacteria 24 hours old a turbid 
suspension in bouillon was prepared. A bouillon culture of the hog-cholera bacilli 
only 24 hours old in which the growth was abundant was also on hand. With these 
cultures three pigs, about 6^^ months old, of the same breed and lot, were inoculated 
as follows : 

No. 462 received into the right lung one-fourth cubic centimetre of the swine- 
plague suspension, and three-fourths cubic centimetre of the hog-cholera bouillon 
mixed. 

No. 463, inoculated in the same way with twice this quantity, i. e., one-half cubic 
centimetre swine-plague and 1| cubic centimetre hog-cholera culture. 

No. 461 received 5 cubic centimetres of the hog-cholera culture alone into the right 
lung. 

No. 463 was dead next morning, within 16 hours after inoculation. Animal in good 
condition ; weight 72 pounds. Subcutaneous fat reddened. Blood oozes from the 
cut vessels and coagulates feebly. Arborescent injection of minute bloodvessels 
of connective tissue in axilla and between muscles on thorax. In abdominal cavity 
a considerable quantity of yellowish serum. Ventral portion of spleen imbedded 
in an elastic whitish exudate. Costal and diaphragmatic pleura show intense 
vascular injection. In right pleural sac about 140 cubic centimetres blood-stained 

* It must be borne in mind that the various attenuations of hog-cholera and swine- 
plague bacteria can not be individually considered with reference to their pathogenic 
effect iu a tabulated form ; we must refer to the text for these. 



107 

liquid, ill loft 70 cubic centimetres. Lungs but partly collapsed : nulematous. Over 
the entire right lung a very thin friable exudate; over the loft this is found only 
on most dependent portion. Kiglit lung punctured by needle in principal lobe. The 
puncture shows as a hemorrhagic spot. 

In the stomach — which is filled with food — and in intestines, nothing abnormal. 
Kidneys with base of pyramids darii red. Spleen slightly enlarged. 

In the spleen pulp only swine-plague bacteria detected. In an agar culture there- 
from no motile bacilli seen. A bouillon culture from the peritoneal exudate contains 
only swine-plague bacteria. Cover-glass preparations from both pleural and perito- 
neal exudate show numerous polar stained bacteria. 

No. 402 manifested labored breathing soon after the inoculation. It lay on its 
bedding unable to get up. It was found dead May 16. 

Considerable reddening of the skin on ventral aspect of body. Subcutis as in 463. 
In abdominal cavity a small quantity of yellowish serum and some iibrinous coagula. 
Spleen quite large, congested and friable. 

Thoracic cavity. Right pleural sac contains 100 cubic centimetres of turbid dark 
red fluid. Considerable friable exudate covering costal and pulmonary pleura of this 
side, especially abundant on small lobes. Pleura opaque, thickened and wrinkled. 
Both cephalic and ventral lobes not enlarged, but firm, on section grayish red, solid. 
Bronchioles tilled with whitish muco-pus. The needle puncture in principal lobe is 
the center of a hepatized mass, fully 2 inches in diameter; on section some lobules 
bright red, others hemorrhagic, dark red. Nearer periphery of this mass the hepa- 
tization is grayish red ; the interlobular and peribronchial tissue appear as irregular 
grayish lines. lu the left lung the priucipal lobe congested; slight interlobular 
(edema. Along cephalic border, under pleura, a dark red hepatized mass, about one- 
half inch in diameter. Tip of ventral lobe adherent to pericardium, beneath adhe- 
sions small foci of dark red hepatization. In terminal bronchi adult lung worms. 

Pericardium adheres to heart surface by means of a thick yellowish pseudo-mem- 
brane. Glands along posterior aorta hemorrhagic. 

Digestive tract : Stomach empty. Mucosa thrown into folds and covered with an 
abundance of very viscid mucus. In fundus it is congested. Hypera-mia also ai'ound 
cardiac expansion. Duodenum pigmented. Mucosa of ileum swollen and sprinkled 
with small hemorrhagic spots. Mucosa of ca'cum and upper colon discolored. In 
lower colon minute whitish spots, with injected margin, evidently superficial ulcers. 
Meso-colic glands enlarged, hypera>raic. 

Liver somewhat enlarged, quite firm. Acini slightly projecting ; some dark red; 
in most of them intralobular necrotic masses, the result of some former disease.* 
Portal glands enlarged and hypenemic. Kidneys congested; pyramids dark bluish 
red. Glomeruli just visible to naked eye as injected points. 

Bacteriological examination : In cover-glass preparations from the hepatized mass 
of right principal lobe very many swine-plague bacteria and a few somewhat larger 
forms. In two agar plates from the same region large number of colonies of two kinds 
appear. One represents swiue-plague about ten times more numerous than the hog- 
cholera colonies, which are on second day twice as large. In cover-glass prepara- 
tions of spleen pulp a considerable number of bacteria appearing as hog-cholera 
bacilli. The same is true of the liver. Agar plates from each organ contain only 
colonies of hog-cholera bacilli. 

No, 461, though sick for a few days, fully recovered. 

This experiment illustrates the greater rapidity of action of swine- 
plague bacteria even in small doses. It also demonstrates their greater 
virulence, for the pig inoculated with a large dose of hog-cholera bacilli 

* This condition of the liver will be discussed in a subsequent publication. It bears 
no relation to the inoculation, since it ia found in swine otherwise healthy. 



108 

alone, altliougli sick for a few days, recovered. Another fact of im- 
portance illustrated in these cases is the slow action of hog-cholera 
bacilli in invading otber organs. Thus the swine-plague bacteria had 
killed No. 463 before the hog-cholera bacilli had invaded the spleen 
and liver. In No. 462, however, enough time had elapsed to permit the 
hog-cholera bacilli to spread through the body while the swine-plague 
bacteria were now limited to the lungs. The invasive power of hog- 
cholera bacilli, though slower, is nevertheless more lasting. 

There is no evidence to support the view that either swine-plague or 
hog-cholera bacilli may produce serious disease in man. No bacteria 
have thus far been described as the cause of human disease which are 
identical with either of the bacteria of swine disease. Nevertheless 
the possibility of an occasional transmission from animal to man can not 
be wholly set aside until more thorough bacteriological investigations 
of human diseases shall have been made in those localities where infec- 
tious swine diseases are very prevalent. 

It is of interest to note that among human diseases typhoid fever 
bears a close resemblance to hog cholera, not only as regards the gen- 
eral character of the specific bacteria, but also with reference to the 
disease itself. Again the diplococcus of croupous pneumonia in man 
has many points of likeness with swine-plagne bacteria. The general 
pathological effect as well as the tendency to produce various forms of 
disease by localizations, such as pleuritis, pericarditis, meningitis, are 
strikingly similar to the miscellaneous lesions caused by swine plague 
bacteriii. Typhoid fever and pneumonia are not infrequently associated 
in man, thus affording another point of similarity to the frequently asso- 
ciated swine diseases. Another peculiarity which is common to the 
pneumonia bacteria in man and to those of swine-plague is their frequent 
occurrence in the mouth and upper air-i)assages of man on the one hand, 
of swine on the other.* 

* See the following chapter and appendix. 



ATTENUATED SWINE-PLAGUE RlCTEllIA IN SPORADIC CASES OF PNEUMONIA AND 

IN SEPTIC DISEASES OF SWINE, AND IN THE UPPER AIR PASSAGES OF 

HEALTHY SWINE AND OTHER DOMESTICATED ANIMALS.* 

During the iuvcstigatious of the epizootic forms of swine plagne 
described in these pages, bacteria not distinguishable from those of 
this disease were occasionally encountered in sporadic cases of pneu- 
monia. Tlie affected swine were usually those which had been exposed 
to hog cholera or swine i)lague, or mixed outbreaks, or had been inocu- 
lated and had survived. They were kept isohited for a time by them- 
selves or with other cases of similar history, and they generally died after 
some montlis or became so unthrifty that they were killed. Occasion- 
ally they died with some inflammation of the serous membranes, such 
as peritonitis, pericarditis, or pleuritis. In such cases when examined 
swine plague bacteria were as a rule detected. These lesions were 
attributed to injuries which the swine, penned together, inflicted upon 
one another by fighting. If we bear in mind the variety of lesions 
which may be produced by swine plague bacteria when inoculated into 
healthy swine (pneumonia, pleuritis, pericarditis, peritonitis, inflamma- 
tion, and suppuration of the joints, inflammation with exudation in the 
iutestiues), we need not be surprised to encounter them in similar 
affections arising under the usual conditions. 

The sporadic cases of pneumonia were puzzling in so far as it was 
difficult to account for the presence of swine-plague bacteria. These, 
as we have shown, very easily perish by drying, and when in water and 
in media unsuitable for their development. How they can survive for 
weeks and months in the surroundings of swine is inexplicable. To 
find some other explanation I was led to examine the respiratory tract 
of apparently healthy pigs to see if here, in a manner analogous to 
the bacteria of pneumonia in man, they survived and became a poten- 
tial source of infection under certain conditions. The result was posi- 
tive in many cases. Swine-plague bacteria or bacteria not distinguish- 
able from them were found in the nose, at the base of the tongue and in 
the larynx of a certain number of healthy swine. 

* In this chapter no effort has been made to give an historical review of those 
experinieuts made by former observers which demonstrated the occasional vinileuco 
of the saliva of man and animals. The general relationfihip of these bacteria from 
various domesticated animals to swine plague bacteria is, 1 think, brought out for 
the first time in these pages. See also appendix to this report. 

lOG 



110 

The cases which have come uuder our observation may be grouped 
into several classes : 

1. Sporadic pneumonia. 

2. Other aflections, chiefly inflammations of serous membranes. 

3. Older animals having passed through diseases but apparently 
healthy. 

4. Younger animals not known to have been exposed to disease, 

5. Animals entirely free from these bacteria. 

Groups 1, 2, and 3 generally include, in our observations, older ani- 
mals. 

The method used in all cases was the subcutaneous inoculation of 
rabbits with the tissue, secretion, or exudate suspected of carrying these 
bacteria. The inoculations were made in part conjointly with Veterina- 
rian F, L. Kilborne; in part by him alone. Great care was taken to 
prevent infection from external sources. At first only the nasal secre- 
tion was used. This was drawn up with a sterile pipette and then in. 
troduced into the subcutis of the rabbit through a small incision in 
the skin. This method did not seem quite satisfactory, and in a num- 
ber of cases the animal was killed by bleeding, the mouth carefully 
ex])osed from below and mucus collected from the base of the tongue, 
the posterior nares, epiglottis, and from beneath the vocal cords. The 
mucus was placed in a sterile watch glass. The skin of the rabbit was 
freed from hair and thoroughly washed with a solution of mercuric 
chloride 1:500; with flamed scissors, the skin was cut through usually 
on the side of the abdomen, a little pocket formed, and a drop of mu- 
cus put into it with flamed forceps. The incision was either left to 
itself or united with a stitch of sterilized silk. 

These precautious thus prevented any external infection. At the 
same time a prolonged experience in such work leads me to believe that 
swine-plague bacteria are not transmitted in a dried conditiou, excepting, 
perhaps, for a few days only. The outcome of the inoculations also in- 
clined us to exclude any accidental infection. When several rabbits 
were inoculated with mucus from the same locality they either died 
together or both survived. 

The demonstration of swine-plague bacteria in the ui)per air passages 
of swine naturally led to an examination of the air passages of other 
domesticated animals by the same methods. These are reported by 
Dr. V. A. Moore, assistant in the laboratory, to whom this part of the 
work was intrusted. It will be seen from this report that an attenuated 
variety of bacteria, belonging to the group of swine-plague bacteria and 
not distinguishable from them, inhabit the mouth and upper air passages 
of such domesticated animals as cattle, dogs, and cats, and that some 
sporadic diseases among smaller animals, such as rabbits, guinea-pigs, 
and fowls, are caused by the same bacteria. This group has a wide 
distribution, therefore, and may be regarded as a more or less common 
inhabitant of the mucous membranes. 



Ill 

111 tbo followiug brief synopsis of the cases illustrative of the above 
statements, tliey are grouped as nearly as possible iu accordance with 
the classification above outlined i 

1. Sporadic pticumonia. — Pig No. 481. Placed in infected Log-cholera pen January 
11, 1888. Since February 1, large sores are observed on the shoulders, attributed to 
bites inllicted by other swino in the pen. It died March 5, very much emaciated. 
In the Ciccum several crater-like ulcerations, involving the muscular coats. In the 
upper colon about a dozen ulcers, one-fourth to three-eighths inch in diameter. 

The ventral and cephalic lobes of both lungs and the roots of principal lobes, also 
foci in median lobe, hepatized, pale red. 

A bit of diseased lung tissue torn up in sterile bouillon and one-fourth cubic centi- 
metre injected into a rabbit. It died in 40 hours, with exudative peritonitis, due to 
swine-plague bacteria. 

Iu this case these bacteria may have come from the other animals in the infected 
pen. In the following case the source is not so obvious. 

No. 492, received at the Station January 25, 1888, with three others (490-493, in- 
clusive). In nialiiug inoculations from the nasal mucus of these pigs, to be described 
later. Dr. Killtorne noticed that the secretion w;i« mucopurulent, while in otlu^r pigs 
handled at the same tiuie it was serous. No. 492 became unthrifty, and died about a 
month after it was brought to the Station. 

The lungs were firmly bound to diaphragm and chest wall by old adhesions. The 
ventral and cephalic lobes, the roots of the principal lobes of both lungs and the me- 
dian lobe airless, iu condition of broncho-pnoumonia. The catarrhal masses in 
the alveoli appeared as a pale grayish yellow, delicate mottling under the pleura. 
Throughout the hepatized portions are yellowish necrotic foci one-sixteenth to one- 
eighth inch in diameter. The smaller bronchi contain a soft, creamy muco-pus. In 
the large bronchi, the mucosa hypenemic. Bronchial glands enlarged, very pale 
and firm. 

Two rabbits inoculated as in prece ding case. One died iu 40 hours, tlie other on 
the third day. Bacteria showing the polar stain present in large numbers in organs 
of the first; iu small numbers in tlie second rabbit. In cultures they are not distin- 
guishable from s-wiue-plague bacteria. 

Pig No. 267, received October 16, 1889. This animal belonged to a lot of swino 
which had been inoculated with attenuated hog-cholera cultures and subsequently 
exposed to hog cholera. The animal died January 2, 1890. In the lungs were regions 
of collapse and broncho-pneumonia, as well as marked bronchitis. From the abun- 
dant mucus in the upper trachea two rabbits were inoculated. They succumbed on 
the fourth and the sixth days, respectively, to an exudative and hemorrhagic peritoni- 
tis characterized by the jiresence of swine-plague bacteria. 

Pig No. 188. This animal was jdaced in an infected hog-cholera pen March 13, 1889, 
and removed iu 5 days. It was killed December 9, after a long period of unthrifti- 
ness. The ventral lobes of both lungs were hepatized, of a grayish-red appeai'ance 
(broncho-pneumonia). The liver covered with bluish and whitish patches, in which 
the interlobular tissue is thickened. This thickening is limited to the surface. One 
rabbii; inoculated with mucus from larynx died in 10 days, with oxteusive subcutane- 
ous purulent infiltration and exudative peritonitis. The only bacteria found were 
the swine-plague bacteria. 

Pig No. 308 was purchased from a neighboring farm February 7. Four days later 
it was killed and hepatization of a portion of both prinicipal lobes determined, to- 
gether with bronchitis of the air tubes leading to these diseased regions. Two rab- 
bits were inoculated from the tracheal and pharyngeal mucus, and one from the 
hepatized lung. The latter remained alive, while the two former died in 3 and 4 days, 
respectively, with extensive exudative peritonitis. The swine jjlague bacteria alone 
were present in the organs of both rabbits. 



112 

Pig No. llii was placed iu an infected hoof-cholera pen January 22, 1889, where the 
swine-plague disease was present. September 2 it was transferred to another pen, 
and killed January 13, 1890. The internal organs were healthy, with the exception 
of the lungs, iu which there were several small foci of collapse and some lung worms. 
One rabbit inoculated with nasal mucus from the base of the tongue died in 3 days. 
There was considerable phlegmonous inflammation and peritonitis as the result of the 
inoculation. The peritoneal exudate contained immense numbers of swine-plague 
germs. The other rabbit inoculated with mucus from below the vocal chords died in 
3 days with the same lesions and bacteria present. 

2. Other affections. — Pig No. 180. This pig was exposed to hog cholera in an infected 
pen March 13, removed March 18. It survived the exposure and was killed June 4. 
Its internal organs were normal with exception of the peritoneal cavity, which con- 
tained a considerable quantity of cloudy serum, the result of peritonitis. Four 
rabbits were inoculated from mucus obtained from below the vocal chords and at the 
base of the tongue. The two inoculated from the latter source died in about 24 
hours. In both the spleen and blood contained largo numbers of swine-plague bac- 
teria. The two inoculated with tracheal mucus died within 36 hours. The spleen of 
both contained large numbers of the swine-plague bacteria. 

Pig No. 202. This animal was fed in May, 1881), with small quantities of culture 
li(iuid containing hog-cholera bacilli twice a day for a week without producing a 
fatal disease. November 15 it was penned with No. 119, which harbored the swine- 
plague germs. February 14 it was killed by bleeding, and two rabbits inoculated 
with mucus from the base of the tongue and from the larynx respectively. Both 
rabbits died, one in 3, the other in 4 days. The lesions consisted in subcutaneous in- 
flammation and exudative, partly hemorrhagic peritonitis. Swine-plague germs 
were present in the various organs, especially in the peritoneal exudate. 

No. 37. This animal had been inoculated in the lungs with a culture of swine- 
plague bacteria, October 8, 1888. January 27, 1889, it was exposed to hog cholera, 
which exposure it survived. It was killed August 16, in a very good condition. The 
only noticeable abnormal condition was the firm adhesion of the right lung to the 
chest wall by means of firm, fibrous tissue, the result of the swine-plague inoculation. 
The lungs themselves healthy. Three rabbits were inoculated with mucus from the 
respiratory passages (tongue, nose, and larynx). All three rabbits died, two in 48 
hours, the third in 4 days. In the latter the inflammation at the jilace of inoculation 
and the peritonitis were most pronounced. In the organs of all three rabbits the 
swine-plague bacteria were present, especially numerous iu the peritoneal exudate. 

The followiug case is of importance, because the bacteria obtained 
from it were tested upon pigs and found virulent. 

No. 164 survived a hog-cholera exposure early in 1886, and in June of the same year 
was transferred to another pen. It was kept until October, 1887, at which time it 
died of peritonitis, probably occasioned by injuries received in fighting with other 
pigs in the same pen. No bacteriological examination was made of the peritoneal 
exudate, but two rabbits were inocnlated with mucus from the trachea. 

One died iu 20 hours ; in the various organs numerous bacteria showing polar stain. 
The other died on second day, with the same bacteria, as demonstrated by the micro- 
scope and cultures iu bouillon and gelatine. 

To test farther the relative virulence of these bacteria a peptone bouillon culture 
was prepared, of which two mice received subcutaneonsly one-twelfth cubic centi- 
metre ; two pigeons received subcutaneonsly and into the muscular tissue one-fonrth 
cubic centimetre ; one guinea-pig received subcutaneonsly one-eighth cubic ceutime- 
tre, and one rabbit one-twelfth cubic centimetre. 

The guinea-pig and the pigeons remained well. One mouse died in 24 hours, the 
other in 3 days. In the first large numbers of bacteria; in the second few. The 
rabbit died within 2 days. In tliis animal there was slight infiltration of skin and 



113 

subcutis at point of inoculation. Peritonitis. Invagination of lower colon. In tlio 
various organs and peritoneal exudate numerous bacteria showing polar stain. 

The pathogenic character of these bacteria was further donioiistrated by inocu- 
lation of swine. 

November 11, 1887. No. 431, 6 weeks old, received into right lung through chest 
wall 2i cubic centimetres of a peptone bouillon culture. 

No. 432, 6 weeks old, received the same. 

No. 433, 6 weeks old, received 5 cubic centimetres subcutaneously. 

No. 433, though affected by the inoculation for a time, recovered. 

No. 431 appeared paralyzed and unable to get up 3 or 4 days after the injection. 
Respirations somewhat quickened. It took very little food. Found dead 14 days after 
inoculation. 

Slight infiltration in subcutis at point of injection. Right lung collapsed. Pleu- 
ral cavity half full of blood-stained serum. Considerable spongy, yellowish exudate 
is loosely attached to the walls of the thorax, the lung surfiice, and the diaphragm. 
The lung tissue is not hepatized excepting a small mass which is necrosed and which 
probably represents the place where the needle penetrated. Left lung not affected, 
closely bound to thorax by fibrous adhesions which give way without much diffi- 
culty. The lymph gland near root of neck very large, whitish on section, small yel- 
lowish foci in cortex and medulla. Slight fibrinous exudate and considerable yellow 
serum in abdomen. In upper and middle portion of colon, the mucosa is covered by 
patches of a very thin grayish deposit, suggesting necrosis of the surface epitheliuiji. 

Cultures from spleen negative; those from pleural exudate show the injected bac- 
teria only. A rabbit inoculated subcutaneously with about one drop of serum from 
the pleural cavity diluted in sterile beef infusion died within 48 hours. No local re- 
action or peritonitis. Innumerable polar-stained bacteria in the spleen, which is 
enlarged, friable. Fewer in the liver ; still fewer in blood from heart. Cultures re- 
vealed the same organism. 

No. 432 breathed with difficulty for several days after the injection. It seemed 
feverish and refused food. Within two weeks it was greatly improved. December 27 
its rectum was prolapsed and it died a week later. At the autopsy the cause of death 
was found to be invagination and rupture of ileum. The lungs presented some inter- 
esting features. The right lung was adherent to thoracic walls and diaphragm by 
means of fibrous tissue not yet very firm. The left lung was adherent in several 
places. The various lobes of the right lung were bound together by fibrous tissue 
and to a tumor lying between principal and ventral lobe along ventral border of lung. 
The tnmor was removed by careful dissection, the lung tissue being slightly con- 
densed and hyperaemic near attachment. There was no hepatization of either lung. 
The tumor felt tense, walls about one-eighth inch thick, inside dark red. Contents 
putty-like, grayish, made up of pus. Pericardium thickened andfittached in several 
places to epicardium, which is likewise thickened, opaque. 

In a gelatine-roll culture inoculated with a particle of the dry pus numerous col- 
onies of the injected bacteria appeared after a week. A rabbit inoculated with a 
particle of pus died in 5 days with considerable local infiltration and enlarged spleen. 
No peritonitis. In the spleen a moderate number of bacteria identified in cultures 
with those originally injected into the pig. 

These bacteria were in every way like the various swiue-plague bac- 
teria with oue exception. In liquid cultures when one or two days old, 
translucent capsules could be seen surrounding the bacteria individu- 
ally when the liquid was examined in the hanging^ drop and the border 
of the drop was carefully scrutinized. This method I have found of much 
service in disclosing the presence of these glassy envelopes when dry- 
ing and staining failed to bring them into view. The bacteria, as they 
1G14 8 



114 

are drawn to the border of the drop, do not touch one another, but re- 
main separated from each other by a space of defiuite width. Careful 
focussing then will also bring out the very faiut outlines of the oval 
transparent capsules. In the inoculations above described, the capsules 
served as an important means of identifying these swiue-plague bacteria 
from case to case. 

3. Older animals apparently healthy hut previously exposed to disease. — 
Under this head would come some of the cases already recorded and 
the following : 

No. 420 had been inoculated with hog-cholera bacilli October 6, 1887, and with 
swine-plague bacteria October 20. March 1, 1888, a drop of mucus takeu from nares 
with a capillary pipette and forced into subcutis of a rabbit through a skin incision. 
The rabbit died in 10 days with exudative pleuritis. the exudate containing swine- 
plague bacteria. 

No. 219. This animal was inoculated subcutaneously with attenuated hog-cholera 
cultures September 27, 1889. It was killed January 13, 1890, and found normal. There 
was at the place of inoculation an encysted caseous mass about 1 inch in diameter. 
Three rabbits were inoculated with mucus from the respiratory tract. Of these but 
one rabbit died on the 11th day with purulent pleuritis and pericaroitis. Swine- 
plague bacteria were obtained from the exudate and their virulence tested by inocu- 
lating a fresh rabbit with a pure culture. 

4. Animals not known to have been exposed to disease. 

October 6. Nasal mucus obtained from the nares of a healthy pig on a ilamed glass 
rod is stirred up in sterile water and one-half cubic centimetre injected subcutane- 
ously into two rabbits. 

No. 1. Dead October 12. Purulent thickening of the subcutis at point of inocula- 
tion and extending thence over abdomen and thorax as a sanguiuolent eli'usion. Per- 
itoneum roughened. A cover-glass placed on caecum, removed and stained, shows 
immense numbers of bacteria exhibiting the polar stain. The same bacteria scarce 
in blood, spleen and liver. 

No. 2. Dead October 13. Lesions as in No. 1. Exudative peritonitis with ecchy- 
moses on ciecum. 

Cultures from both cases on gelatine and in bouillon contain only swine-plague 
bacteria. 

Additional inoculations were made February 2 and March 1, 1888. 
Nasal mucus from supposedly healthy pigs was collected in a capillary 
pipette and a drop forced with a rubber bulb into a subcutaneous pocket 
made by an incision through the skin. The incision was closed with 
collodion. 



Date. 


Rabbit 
No. 


From 
pig No. 


Result. 


Feb. 2 
Feb. 2 
Feb. 2 

Feb. 2 
Mar. 1 
Mar. 1 

Mar. 1 
Mar. 1 
Mar. 1 
Mar. 1 

Mar. 1 


1 
2 
3 

4 
5 
6 

7 

8 

9 

10 

11 


483 
484 
493 

491 
490 
491 

493 

483 

482 
484 

468 


Negative. 

Do. 
Dies in 48 hours. Large numbers of polar-stained bacteria in 

blood, spleen and liver. 
Negative. 

Dies in 7 days. Extensive purulent infiltration of subcutis; cul- 
tures negative. 

Negative. 
' Do. 

Dies in 13 days. Pneumonia and exudative pleuritis. 

Dies in 7 days. Same as No. G. Bacteria obtained from spleen 
in cultures fatal to a rabbit in 48 hours. 

Dies in 13 days. Same as No. 9. 



115 

No. 468 belonged to one lot brought to Station January 4, 1888. 

Nos. 490 to 493, inclusive, to another lot brought to Station January 
25, 1888. 

Nos. 481 to 484, inclusive, to still another lot brought to Station Janu- 
ary 10, 1888. 

The inoculation disease in the rabbits varied considenibly. In one, death ensued in 
48 hours. Nos. 6 and 10 died in 7 days, and in both there was extensive purulent in- 
filtration of subcutis over abdomen and thorax. Finally, in Nos. 9 and 11 there was 
exudative pleuritis with pneumonia. In No. 9, one-half, in No. 11, the whole of the 
left lung hepatized. In the pleuritic exudate aud the lung tissue large numbers of 
polar-stained bacteria. 

None of the three lots of pigs were thus free from these bacteria. It will be noticed 
that the mucus from four pigs was tested twice aud that the results were not uniform. 
No animal produced disease more than once while one failed to produce disease both 
times. 

rig No. 303. January 28, 1890. This animal was taken from a herd which had 
been purchased Jauuarj' 25. The farm from which it came is said to have had some 
form of swine disease on it nearly a year ago. The thoracic organs of the pi"- were 
normal in appearance. Two rabbits were inoculated, one with mucus from the 
larynx, the other with mucus from the pharynx. Both succumbed on the third and 
fourth day, respectively, to exudative peritonitis. In the exudate the swine-pla"-ue 
bacteria were quite abundant. 

December 24, 1890. No. 447, about 4 months old, received yesterday with a lot of 
other pigs from a farm which has been free from disease for several years. The pi"- 
was killed by bleeding, and although it seemed well, the anterior half of both lun"-3 
was found diseased. The diseased lobes were of a pale red appearance and seemed 
cedematous rather than hepatized. There was considerable muco-puruleut secretion 
in the smaller bronchi. In the terminal bronchi of the principal lobe some luu"- 
worras. 

One rabbit was inoculated subcutaneously with a particle of lung tissue and two 
Avith mucus from base of tongue. The former remained well ; both the latter died. 
One died within 40 hours with considerable local purulent infiltration of skin and 
subcutis. Spleen enlarged, containing bacteria showing polar stain. Culture on ao-ar 
from spleen contains only swine-plague bacteria. The second rabbit died in 3 days, 
■with very extensive subcutaneous infiltration and exudative peritonitis. Spleen en- 
larged and dark colored. In the organs few bacteria, in the exudate a large number. 
Cultures from spleen and exudate contain only swine-plague bacteria. In order to 
test the virulence of these bacteria in pure cultures, an adult rabbit was inoculated 
subcutaneously with an equivalent of one five-huudredths cubic centimetre bouillon 
culture diluted in bouillon. The rabbit died on the fourth day with lesions like 
those of the preceding case. 

5. The results thus far obtained must not lead us to infer that all 
swine carry with them bacteria closely allied to swine-plague bacteria. 
Some herds are entirely free from them, as the following statements will 
show : 

Pigs Nos. 116 to 133 were received January 4, 1889, from a place in the District of 
Columbia where swine diseases have not prevailed for a number of years, and where 
much care is bestowed on the rearing of swine. From four of these, nasal mucus was 
collected aud four rabbits inoculated subcutaneously with one or more drops. All 
remained well. 

From another lot of eight, received February 4, two were tested. The results were 
likewise negative. 



116 

To test tlie matter somewhat more thoroughly iu subsequent cases, 
the auimals to be examined were killed and mucus taken from various 
places in the upper air passages. 

No. 205, one of a lot regarded healthy, killed June 15,1889. Pericardium firmly 
adherent to the heart. Three rabbits inoculated with mucus from posterior uares, the 
base of tongue and from below vocal cords. All remained well. 

No. 207, from another lot, killed on the same day. The organs were in general 
healthy with the exception of the large intestine. The mucous membrane appeared 
to be in a state of mucous degeneration. It was swollen, partly translucent. On 
valve and along colon small patches of a thin, friable, yellowish deposit. Five rab- 
bits were inoculated— two from this deposit, three with mucus from trachea, poster- 
ior uares, and base of tongue. All remained well. 

It would be going too far to maintain that all forips of lung disease 
were the result of the invasion of swine-plague bacteria. The absence 
of these bacteria is well illustrated by an outbreak of hog cholora in- 
vestigated in the fall of 1887, and reported in the special report on hog 
cholera, pp. 39-52. 

In about one half of the fifty cases there was some disease of the lungs. 
This was in part simple collapse, in part broncho-pneumonia involving 
one of the small ventral lobes. Of the sixteen rabbits inoculated with 
particles of diseased lung tissno from sixteen cases, four survived and 
the remainder died of hog cholera. Swine-plagiie bacteria were not de- 
tected. It is reasonable to assume that if they had been present in the 
upper air passages they would have sooner or later invaded the diseased 
lung tissue and appeared in the inoculated rabbits. 

In addition to the foregoing experiments a few inoculations into rab- 
bits were made with mucus from the coecum of healthy pigs, but they 
were negative so far as swine-plague bacteria are concerned. The 
mucus was taken from the crypts on the ileocecal valve and the sur- 
face of the patch in which they are imbedded. 

Ciecum No. 1. One rabbit and two mice inoculated subcntaneously. No result. 

CtecumNo. 2. One rabbit inoculated. Died iu 8 days. Extensive sauguinolent and 
purulent inflammation of the snbcutis of abdomen. Peyer's patches swollen and pig- 
mented. The appendix of caecum swollen, blackish; ulceiB on mucous surface. Cul- 
tures from iuternal organs wholly negative. 

Cfecum No. 3. One rabbit inoculated. Died in 8 days. Snbcutis and appendix as iu 
preceding case. Cultures sterile. 

Ciecum No. 4. One rabbit inoculated. Died in 11 days. On thigh, an abscess be- 
tween muscles half as large as a hen's egg. Center disintegrated iuto a curdy mass. 
No other lesions. In the pus of abscess large numbers of bacilli of various lengths, 
staining feebly. They fail to grow in culture media. Internal organs free from 
bacteria. 

It may be claimed that the presence of swine-plague bacteria on the 
mucous membranes of healthy swine and other domesticated animals 
is an argument against the specific character of swine-plague bacteria, 
and hence against the existence of a specific disease induced by them. 
We have already met this argument by the numerous successful inocu- 
lations of swine-plague bacteria into healthy swine, by which a disease 



117 

like the natural disease has been jirodaced. The attenuated virulence 
of the bacteria in the air passa<j;es makes it probable tliat few of them 
arc able to produce disease excepting in a secondary role. 

There are two infectious diseases in man which in this respect offer 
some striking analogies to swine plague. The disease known as croup- 
ous pneumonia is chiefly associated with bacteria {DiplococeuH pneu- 
monuv) bearing much resemblance to swine-plague bacteria. Those 
bacteria are now regarded as the chief, if not the only, cause of pneu- 
monia. Strangely enough, bacteria not distinguishable from these are 
occasionally encountered in the saliva of healthy persons. Senator, 
Pasteur, and Sternberg wore among the first to call attention to the 
fact that rabbits inoculated with s[)utuni may die of septicemia, and 
the bacteria found in the internal organs of these rabbits were identi- 
fied subsequently with the bacteria of pneumonia. We have thus a 
complete analogy between swine-plague and croupous pneumonia. 

In another disease facts of similar nature have recently'' come to 
light. Roux and Yersin* have found in the mouths of about 10 per- 
cent, of all healthy persons examined bacilli which have no pathogenic 
effect, but which resemble closely the bacilli of diphtheria, which, in 
fact, they regard as very attenuated forms of the diphtheria bacillus. 
Loftier and others had previously found similar bacilli in the mouths 
of healthy persons. 

There are several important questions raised by the discovery of at- 
tenuated forms of disease-germs in the surroundings, and in the body 
of animals. Do these bacteria belong to the same species as the viru- 
lent forms, and, if so, can they gain virulence enough under certain 
circumstances to produce disease? That pathogenic bacteria may gain 
in virulence has been shown by Pasteur, Koux, and others. Whether 
this applies to all kinds of disease-germs may be reasonably doubted, 
and the experiments thus far tried by us to increase the virulence of 
attenuated hog-cholera and swine-plague bacteria have shown that by 
l^assing them through susceptible animals no decided increase in viru- 
lence is observed. On the other hand, so far as methods are able to 
inform us, these same attenuated bacteria found in the air passages of 
healthy animals, and the swine-plague bacteria proper found in disease, 
do belong to the same species, and must be regarded as simple varieties. 

These discoveries also point out that the one property of pathogenic 
bacteria which must receive special attention is their relative virulence. 
This seems to be the one factor which determines the severity and the 
communicabilit}' of infectious diseases. 

• Auuales de I'lustitut Pasteur, 1890, p. 409. 



BKIEF REVIEW OF THE INVESTIGATIONS OF OTHER OBSERVERS. 

AMERICAN. 

Of the work done in investigating the diseases of swine that of Dr. F. 
S. Billings seems to liave aroused much attention, chiefly because of the 
polemical attitude which he has assumed and the iieculiar manner in 
which he has criticised the work of the Bureau of Animal Industry. 
His results are contained in a volume of 4L4 pages, published by the 
CJniversity of Nebraska in 1888, in connection with which institution 
the work was carried on. 

In this volume Billings has given us very little opportunity to dis- 
cover how much work was actually done in arriving at the various theo- 
ries and conclusions contained in the volume. The statements of ex- 
periments are exceedingly meager and the bacteriological work very 
unsatisfactory. 

It is evident that in work of this kind the discovery of the causes of 
disease is the fundamental problem, and all other problems must at the 
outset be subservient to this one. The bacteriological work is there- 
fore the most important. A perusal of the report of Billings shows that 
he has contributed nothing whatever to the elucidation of this problem, 
while his obstructive attitude has confused and retarded the progress 
in the right direction in a marked degree, as the following statements 
conclusively prove : 

He has assumed the position that there is but one infectious swine 
disease in the country, while the investigations of the Bureau of Ani- 
mal Industry have maintained that there are at least two. The various 
criticisms which Billings has written of the work of the Bureau need not 
engage our attention here. They are interesting enough ro be read in 
the original, but they all collapse in view of investigations published 
in the present volume. That the earlier investigations of the Bureau 
on swine plague were not absolutely demonstrative no one will deny. 
That they, however, pointed very directly to another disease is shown 
by pathological as well as bacteriological considerations — a severe 
pleuro-pueumonia associated with specific pathogenic bacteria easily 
differentiated from the bacteria causing hog cholera. The repeated 
occurrence of pathogenic bacteria in case after case of an outbreak could 
not well be overlooked or exjilained away by any patliological consider- 
ations. The duty of an investigator in another section of the country 

118 



119 

would have been the careful investigation of his own territory as to the 
presence or absence of such diseases. 

What is the nature of the bacteria described by Billings as the cause 
of the infectious swine diseases ? 

If we examine pages 103-llGof his report we shall find a brief ac- 
count of the bacteria in question. If we examine his description and 
figures on page 10-4, and compare them with the swine-plague bacteria 
described in the foregoing pages, it will be observed that he has before 
him swine-plague bacteria and not hog-cholera bacilli. Of this he seems 
to be himself aware, for on page Jll he states that the hog-cholera 
bacteria, as described in the reports of the Bureau, have no existence, 
i. e., are fictitious. 

Next, the growth on potato as observed by Billings is anything but 
that of swine-plague bacteria. It may be that of hog-cholera bacilli or 
of allied intestinal bacteria. 

The remarks about gelatine cultures may apply to at least a dozen 
species of bacteria. 

The observations about the movement of these bacteria is equally in- 
definite. It might apply very well to the Browniau motion of swine- 
l>lague bacteria, but it certainly does not describe the rapid motion 
across the microscopic field so characteristic of hog-cholera bacilli.* 

This very incomplete description of the bacteria found by Billings 
leaves us, therefore, entirely in the dark. The form, mode of staining, 
and the motility, apply to swine-plague bacteria, the potato growth, 
perhaps, to hog-cholera bacilli. How can we reconcile this conflicting 
account ? Bearing in mind the fact that in the organs of swine which 
have succumbed after extensive lesions of the lungs and large intes- 
tine, it is not an uncommon thing to find various forms of bacteria, 
hncillus coli, non-motile bacilli (also found in intestines), streptococci, 
gas-producing, spore-bearing bacilli, etc., either alone or associated 
with the real cause of the disease, we find ourselves unable to explain 
his discovery because we have no full and accurate report of investiga- 
tions actually carried out. The description he gives may apply so far 
as we know to the bacteria found in one hog, in five hogs, or in a hun- 
dred hogs. It is obvious that the amount of conviction his statements 
carry depends entirely upon the number of animals to which such state- 
ments apply. 

An explanation which covers the ground of the statements made by 
Billings fairly well is one which takes into account the mingling of two 
diseases. Since 1886 we have seen very few outbreaks of hog cholera 
not associated with swine plague. The investigations recorded in these 
pages show how frequently it may occur that a culture may contain 

*In his report on the " corn-stalk" disease of cattle, page 18G, Billings seems to 
have lost his doubts concerning the motility of the hog-cholera (swine-plague of 
Billings) bacillus. He there considers it by comparison "to possess most active 
movemeuta." 



120 

both swine-plague and hog cholera bacilli, or that the cultures from one 
animal contain only swine-plague bacteria, those from another of the 
same herd only hog-cholera bacilli. Again this report illustrates that 
we may be called upon to investigate an outbreak of swine disease in 
which hog cholera bacilli are demonstrable in every case, and iu the 
succeeding one we may find only swine plague bacteria or a mixture of 
both germs. 

It is highly probable that Billings had under observation now one 
germ, now another, and occasionally a mixture of both. With this ex- 
planation* iu mind we may easily interpret the conflicting account of 
the bacteria given by Billings, especially if such statements are based 
on a small number of cases only. This explanation is the more plaus- 
ible when we turn to the method used by Billings iu obtaining pure 
cultures from animals. While, on the one hand, his cultivation methods 
"were insufBcieut to determine accurately whether cultures contain more 
than one organism or not, he unwittingly assumes,, on the other hand, 
first, that the bodies of diseased swine always contain only one kind of 
bacteria, and, second, that this kind is always the same. These as- 
sumptions anyone will recognize on reading page 103 of his report. 
How much information can be obtained by such deductive method of 
l)ursuing a most inductive branch of scientific investigation, the reader 
must be allowed to judge for himself. It may be noted, however, that 
such vicious methods furnish ample material for the attack upon work 
done by others. 

Again, the examination of 5 hogs, or of 500 hogs, made over a lim- 
ited territory with a uniform result, does not permit us to generalize 
negatively on the swine diseases of the remaining millions scattered 
over the whole country. This attitude is to be regretted the more 

* A good illustratiou of the iilansibility of this theory may be foimd on pp. 191-197 
of the report of Billiugs, whei'e the results of some iuocnlatioua of smaller auimals 
are detailed. These may be tabulated. 

One rabbit, iuocukited with ouo-half cubic centimetre bouillon culture, subcu- 
taueously, May 14, dies in 3 days. 

One squirrel, inoculated with one-half cubic centimetre bouillon culture, subcu- 
taneously. May 14, dies in 3 days. 

One rabbit, inocuhited with one-fourth cubic centimetre spleen emulsion of preced. 
iug rabbit, May 17, dies in 6 days. 

One rabbit, inoculated with seven drojis of blood, etc., from pig, subcutaneonsly. 
May 23, dies in 1| days. 

In this series the dose injected into the first rabbit is too large to bring out the 
diiiereutial characters of either hog-cholera or swine-plague germs. In the second 
rabbit death was probably due to hog-cholera bacilli. In the third it was certainly 
due to swine plague, since the most virulent hog-cholera bacilli would not destroy 
rabbits iu the dose used, iu less than 4 to 7 days. In the report on the corn-stalk dis- 
ease already referred to (1889), Billiugs states that a certain germ could not " be 
that of swine plague (hog cholera) on account of its acute fatality." These later 
opinions are refreshing in being iu the right direction as far as hog cholera is con- 
cerned. 



121 

wlieii we reflect on tlie fact tiiat the area of diseases is largely (lefined 
by geographical, climatic, aud economic factors. 

In his report, Billings throughout denies the existence of the hog- 
cholera bacillus first described in the Bureau Report for 1885. This 
denial may be found scattered throughout the report. Then we must 
assume that he considered the swine-]>lague bacteria as the cause of 
American swine diseases. This assumi)tion is proven by his repefited, 
almost continuous, discussion of the European iSchiceineseuchenixdWild- 
seiiche.* This continual dragging in of the work of European observers 
can only be understood by assuming a great similarity or a possible 
identity between the bacteria in the hands of Billings and those of 
Schireineseuche, as described by Lol'ller, SchiltZ; lliippe, and others. On 
the other hand, the pathological appearances in these diseases differed 
so greatly that Billings found it necessary to occu])y the greater part 
of his report in needlessly pointing out likenesses and dilferences. 

Up to this point, then, it seems that Billings regarded his swine dis- 
ease bacteria as the same morphologically witb the German Wiklseuche, 
aud that he denied the existence of the hog cholera bacillus. Mean- 
while we studied his publications and made every effort to determine 
what bacteria he was studying, but without success, owing to the im- 
l)erfect diagnosis given and the i)eculiar intermingling of the ])roper- 
ties of the bacteria of hog cholera and swine plague found in bis report. 

In 1889, however, to our surprise, the commission appointed to throw 
some light on this matter found Billings in possession of real hog-chol- 
era bacilli. Cultures were sent by him to Berlin, where a comi)arison 
of these cultures with some sent from this laboratory likewise demon- 
strated that his swine-plague bacteria were identical with the hog- 
cholera bacilli discovered in the Bureau laboratory in 1885,t nearly a 
year before Billings began his work in Nebraska. 

All these facts make it highly probable that Billings had unwittingly 
studied at least several kinds of bacteria, among which the swine-plague 
bacteria of this report must have played an important part. In a recent 
article! on swine diseases, prepared under Hiippe, the author mentions 
the fact that Billings had sent cultures at two different times, which, 
though considered by the sender as identical, were really quite differ- 
ent. In another article Caueva,§ working under Hiippe in Fresenius' 
laboratory, endeavors to group the various bacteria ])roducing swine 
disease, and in so doing separates the bacteria sent by Billings from 
hog-cholera bacilli, because the former were less acti\ely motile, coagu- 
lated milk, and produced only local reaction after subcutaneous inocu- 
lation. They also failed to infect by feeding. While these bacteria 
may represent an attenuated variety of hog-cholera bacilli so far as their 

* Compare also page 141 of tins report, 
t Froscb. Zeitsclirift fiir Hygiene, ix, S. 235. 
tBiinzl-Federn. Archiv f. Hygiene, xii, S. 198. 
$ Centralblatt f. Baliteriologie, IX, 8. 557. 



, 122 

virulence is concerned, none of the hog-cliolera bacilli from numer- 
ous and widely separated localities examined in this laboratory ever 
produced coagulation of milk. Bacteria of the latter class are chiefly 
harmless intestinal parasites which closely resemble hog-cholera bacilli 
{bacillus coli) and which occasionally appear in cultures from cases of 
swine disease. 

If, therefore, Billings had found the hog-cholera bacillus the question 
arises : Why did he fill up his report with pages of extracts, comment, 
and criticism of the European Schweineseuche, when the bacteria of hog 
cholera and SchweineseucJie are wholly different, as every observer has 
admitted who has compared them ? Such discussions are not only use- 
less, but misleading, when brought to bear upon the condition of things 
in our own country. In view of these facts the question also arises: 
Why did Billings so vehemently oppose the hog-cholera bacillus 
described in the Bureau Eeport of 1885, and found by us to exist in 
Nebraska before Billings entered upon his work there, if he had it 
under observation himself? These contradictory positions can only be 
interpreted by the assumption made above, that Billings had at first 
one or several kinds of bacteria under observation differing from the 
true hog-cholera bacillus. 

If we are nevertheless to conclude that Billings has finally settled 
upon hog-cholera bacilli as the cause of swine disease in Nebraska, any 
further comment on his work could only be taken up under hog cholera. 
The question whether there is another disease besides hog cholera is 
settled in the affirmative by the work reported in these pages. This 
second disease seems to be in fact the disease which Billings has had 
in mind in his controversies, and his criticisms of American and for- 
eign work. Unfortunately, however, it has turned out that he has 
mistaken the disease, and now his opposition strangely enough has 
shifted towards the swine-plague bacteria, since an attitude of opposi- 
tion towards hog cholera could no longer be maintained.* 

It is clear to any unbiased reader that work which fViils to grasp any 
positive truth, and is continually shifting its base to avoid the necessary 
consequences of serious errors, and which goes beyond its confines not 
only to criticise, but to discredit in every manner possible the work of 
other observers, can not be seriously taken into consideration as advanc- 
ing in the least degree our positive knowledge. 

During the years 1887-'89, Professor Welch, in conlunction with A. 
W. Clement, V. S., and F. L. Kussell, V. S., investigated a number of 
outbreaks of swine disease in the neighborhood of Baltimore, Md. In 

» A simple atatement of the position of Billings would read thus : 

1. Opposition to hog-cholera bacteria discovered in Bureau laboratory in 1885. 
i^vulence in his writings all points to swine plague. 

2 Discovery by commission and German observers that his germ and the hog- 
cholera bacillus are identical ; hence, 

3. Opposition to swine-plague bacteria. - 



123 

a preliminary report published in the Johns Hopkins Hospital Bulletin, 
December, 1889, Welch gives a brief summary of the results obtained 
up to that date. These investifjators encountered in some herds oid^- 
liog-cholora bacilli, in others only swine-plague bacteria, and in still 
others both kinds of bacteria. They have not been able to fix upon 
any anatomical differences between the herds in which hog-cholera ba- 
cilli were found and those in whicli only swine-plague bacteria were de- 
tected, for in all cases intestinal lesions were present. The description 
of the two kinds of bacteria agrees in every respect with that published 
in the various reports of the Bureau of Animal Industry since 1885. 
With both the authors were able to produce disease in swine, intestinal 
lesions with hog-cholera bacilli and lung lesions, associated with inflam- 
mation of the serous membranes, with swine-plague bacteria. 

While the results agree in every particular with those obtained by us, 
Welch expresses himself with caution concerning the role of swine- 
])lague bacteria, because in the herds studied none were free from intes- 
tinal lesions. He suggests the possibility of overlooking hog-cholera 
bacilli because they may remain limited to the intestinal tract, a possi- 
bility to which we have called attention in the report for 1887-'88, and 
in these pages. On the other hand the facts that pneumonia may be 
jiroduced by swine-plague bacteria, and that a swine disease exists in 
Germany in which j^neumonia without intestinal lesions is associated 
with swine-plague bacteria, " suggest that this organism is also the 
cause of a similar affectiou in this country." 

In 1889 and 1890 Dr. J. A. Jeffries* made bacteriological observa- 
tions in several outbreaks of swine disease of an infections character. 
In one pig -were found a large spore-bearing bacillus, a short bacillus, 
and swine-plague bacteria.t The short bacilli Jeffries found non-path- 
ogenic, while the third form, the swine-plague bacteria, he considers 
the cause of the disease. 

The description of the pathological appearances of the diseased pigs 
and of the swine-plague bacteria found by him, taken together with the 
inoculation experiments and the absence of hog-cholera bacilli, make 
it pretty certain that the disease was identical with that described in 
these pages. 

Through the kindness of Dr. Jeffries a culture of the swine.plaguc 
bacteria was sent to the laboratory, where a comjiarative study of the 
morphological and i)athogenic characters showed them to be an at- 
tenuated variety of swine-plague bacteria, not distinguishable from 
those described in these pages. A few of the inoculations on rabbits 

* Etiology of two outbreaks of disease among hogs. The Journal of Corap. Medi- 
cine, December, liidO. 

tThe spore-bearing bacillus I have found in many outbreaks as the result of post- 
mortem growth. In some pigs sections from every organ show these long wavy fila- 
ments filling up the capillaries and penetrating the tissue in all directions. See also 
page 80 of this report. 



124 

are given to illustrate the variety of lesions which these bacteria may 
produce. 

Tho culture was first tested by plate cultures and two rabbits inoculated from a 
bouillon sub-culture. 

June 3, 1890. One rabbit received oue-eightb cubic centimetre subcutaueously, and 
one one-eighth cubic centimetre into an ear vein. 

In both the temperature was between 105-^ and 106° F. on the sixth day. On the 
tenth day the first had recovered; the second, unable to move hind limbs, was chloro- 
formed. The only lesions observed were two abscesses, one on the right tarsus, the 
other on left elbow joint, both communicating with the joint cavity. 

The culture was thus considerably attenuated. Nothing more was done till Decem- 
ber, when the same culture, passed through a series of agar tubes meanwhile, was 
used, because attenuated, for some preliminary immunity experiments on rabbits 
The virulence of the bacteria was much greater now, as the following inoculations 
prove. Attention is called to the great variation in the lesions produced, and to the 
pneumonia in No. 5. 

December 8, 1890. Two rabbits (Nos. 1, 2) received subcutaueously one-eighth cubic 
centimetre bouillon culture, and two (Nos. 3, 4) the same dose into an" ear vein. 
No. 1 dies in 7 days with extensive purulent infiltration of the subcutis over abdo- 
men and thorax, purulent peritonitis and pleuritis. 
No. 2 survives. 

No. 3 very sick on the fifth day and chloroformed. A subcutaneous purulent in^ 
filtration extends from place of injection on the ear over the greater part of face. 
No other lesions observed. 

No. 4. Temperature on third day 105.5° F. Dies on the fifth day with peritonitis 
and pleuritis. The exudate stretches in the form of delicate grayish viscid threads 
between coils of intestine when these are lifted up, and from chest-wall to pleura of 
lungs. The exudate a mixture of leucocytes and immense numbers of bacteria. 

As these experiments were designed to find a dose which would not prove' fatal 
they were repeated. 

December 16. Two rabbits (Nos. 5, 6) receive a subcutaneous injection of one-eight- 
hundredth cubic centimetre bouillon culture, and two (Nos. 7, 8) an intravenous in- 
jection of the same dose. 

In all cases the culture was diluted and one-fourth cubic centimetre of the dilution 
injected. 

No. 5 dies in 9 days. Extensive purulent infiltration of subcutis over abdomen and 
part of thorax. Exudative peritonitis absent. Purulent pleuritis with exudate es- 
pecially abundant on right lung and chest-wall. Hepatization of the two small anterior 
and portion of principal lohe of same side. The hepatized lobes in part dark red and 
pale red, firm and enlarged. Epicardium covered with a membranous exudate. In 
the exudate numerous bacteria showing the polar stain. 

'No. 6. Temperature on second day 105° F. Dies on sixth day. Extensive purulent 
and sanguinoleut infiltration of the subcutis as in preceding case. Spleen barely en- 
larged, somewhat darker than normal. No peritonitis or pleuritis. 

No. 7. Temperature 105.2° F. on second day. Dies on thirteenth day. Extensive 
subcutaneous infiltration as in preceding case. Straw-colored, elastic membranous 
exudaie on liver, spleen, and ca;cum, and between coils of large intestine, mattino- 
the various organs together. The exudate is easily pulled away and consists of fatty 
pus cells and immense numbers of swine-plague bacteria. In pleural sacs some 
serous exudate. Pale red hepatization of a small portion of the small anterior lobes 
of right lung. Spleen moderately enlarged, dark. Peyer's patches pigmented. 

In Kovember, 1890, Prof. T. J. Burrill, of Illinois University, sent 
two agar cultures of bacteria obtained from an outbreak of swine dis- 



125 

ease in Illinois. Both cnltures were carefully examined and found to 
contain only swineplaffuo bacteria. To test the pathogenic character 
two rabbits were inoculated. These inoculations prove the essential 
identity of these bacteria with swine-plague bacteria. 

November?. From a bouillon culture, 1 day oltl, oue-touth cubic centimetre was 
injected under the skin of a large rabbit. 

November 11. Rabbit found dead this morning. At point of inoculation purulent 
thickening of the subcutis. Ciccnm, colon and rectum sprinkled with hemorrhages. 
Slight viscid exudate on '■tocum which contains largo numbers of the injected bac- 
teria. Liver and kidneys pale. Spleen barely enlarged, dark in color. The agar 
and bouillon cultures from blood, spleen, and abdominal exudate contain only the in- 
oculated bacteria. 

November K5. A rabbit received subcutaneously on side of abdomen one-tenth 
cubic centimetre bouillon culture prepared from the second original culture. Rab- 
bit dies in 40 hours. A very slight infiltration at the place of inoculation. Spleen 
slightly enlarged and engorged. In it a considerable number of s wine-plague bact- 
eria showing the polar stain. Au agar culture from the spleen contains these 
bacteria only. 

GERMAN. 

Of great interest and importance to us are the German investiga- 
tions of swine plague {Sclnveineseuche), because this disease does not ap- 
pear to be complicated with any other disease, as is the case in our own 
country where swine plague and hog cholera are so frequently asso- 
ciated with each other. 

Probably the first inv^estigation in which swine-plague bacteria were 
observed is that of Loftier.* Only one pig was encountered in the 
course of a series of investigations on the continental disease of swine, 
known as rouget and Rothlauf, in which these bacteria were found, hi 
this case the lesions are given as follows : 

The skin of abdomen, Sexual organs, and neck of a livid red ; enormous oedema of 
the (sub) cutis of the neck, extending backwards between forelimbs. Pharynx red- 
dened and swollen. Laryngeal and tracheal mucosa intensely dark red. Lungs but 
slightly affected ; ou the right some dark red regions, containing but little air. 
Nothing abnormal abont the heart. Cloudy swelling of liver and kidneys. Mucosa 
of stomach and upper portion of duodenum intensely reddened. Remainder of intes- 
tines unchanged. Mesenteric glands not enlarged. Spleen rather large, dark bluish 
red, quite firm. 

The bacteria obtained from this case resembled those of rabbit septi- 
cfemia.t They killed inoculated rabbits and mice in 24 hours. Cruinea- 



* Arbeiten a. d. kaiserlichen Gesundheitsamte, I (1885), S. 51. 

t The term rabbit septicjemia originated in a series of experiments on rabbits by 
Gaftky, in 1881 {MittheUungen a. d. kaiserl. Gesundheitsamte I, 1881, S. 102), who pro- 
duced in these animals by the injection of polluted -water a rapidly fatal disease 
caused by bacteria closely resembling those of swine plague and some other animal 
diseases. (See p. 141 of this report.) The writer found bacteria causing septic dis- 
eases in rabbits, probably identical with these in 1886 (Journ. Comp. Med. and Sur- 
gery, Jan., 1887). Prior to Gaffky's work, R. Koch and Davaine had been experi- 
menting with a similar disease in rabbits. 



126 

pigs lived from 2 to 3 days after iuoculation. lu all there was extensive 
sero-sanguinolent infiltration of the subcatis, starting from the place of 
inoculation and extending in some over thorax and abdomen. In one 
the intestines were covered with a sanguiuolent and fibrinous exudate. 
Of three pigs inoculated (probably with minimum doses) one died in 
2 days with the following lesions : 

Skin of abdoineu bluish red; euormons oedema of skin ; luugs hypostatic ; mucosa 
of stomach deeply reddened ; spleen unchanged; kidneys parenchymatous; mesen- 
teric glands not swollen. 

This first reported case is interesting in that the lungs were not the 
seat of disease. 

The disease of tichweineseuclie was established in a more definite man- 
ner by Schiitz in investigations carried on in 1885.* 

Since then it has been generally recognized as a disease distinct from 
Rotlilauf. The material with which Schlitz worked at this time con- 
sisted of — 

1. The stomachs, spleens, and livers of three pigs, more or less decom- 
posed, June 15, 1885. 

2. The stomachs and spleens of several pigs, August 27, from Putlitz. 

3. The trunks of two pigs, November 19, from Putlitz. 

4. Two entire pigs, December 13, from Putlitz. 

In a footnote the author states that several additional cases of this 
disease had come under his observation subsequently. 

In the four pigs of which Schiitz was enabled to examine the viscera, 
all were affected with more or less hepatization of the lungs associated 
with lileuritis, more rarely with pericarditis. In one of these four cases 
there was found, in addition to lung disease, peculiar caseous degen- 
eration of the joints of the limbs, involving the bones and surrounding 
muscles. The various lymphatic glands were greatly enlarged and con- 
tained cavities filled with grayish yellow, semi-liquid masses.t In the dis- 
eased lungs were disseminated yellowish necrotic foci varying in size. 

From all the cases examined bacteria were obtained which were evi- 
dently the same. Schiitz described them as follows: 

When stained with gentian violet they show in their central portions an unstained 
region surrounded by a layer stained blue. The thickness of this layer is greater at 
the poles, so that the extremities appear more deeply- stained than the sides. When 
deeply stained they appear uniformly blue. As these organisms stand between mi- 
crococci and bacilli, they may be called bacteria. They are 1.2 // long and 0.4 /x to 0.5 
H broad. They multiply in the following manner: They become twice as long as 
broad; show distinctly rounded extremities, and stain like the organisms of rabbit 
septicicmia and fowl cholera, so that between the deeply stained ends about one-half 
or a third of the entire length remains unstained. Careful examination shows, how- 
ever, that the colored end pieces are connected with each other by a fine line which 
passes from one to another on each side. The end pieces then separate and the me- 
dian portion disappears. The former are at first spherical, but very soon assume an 
oval form. Hence from every organism two new individuals arise by division, in 

" Loc. cit., I (1885), pp. 376-413. 

t Compare cases on p. 75 of this report. 



127 

which by careful staiuiug the uncolored ceutral portion is easilj' distingnished from 
the colored periphery-. If the process of multiplication is very rapid, as in pigs and 
rabbits, the organisms do not attain the size given above, but divide before the un- 
stained median piece bcconios distinctly visible. Under these circumstances the or- 
ganisms of the succeeding generations are smaller, only one-half as large as, or even 
smaller than, those which have resulted from the slow division of the bacteria. The 
younger generations are frequently extraordinarily small, plainly oval, however, and 
staiuiug uniformly in gentian violet. They do not execute any spontaneous move- 
ments. 

These bacteria were fatal to mice, rabbits, and gninea-pios. Pigeons 
succumbed to large doses. Fowls and rats were not susceptible. A 
comparison of the virulence of these bacteria obtained from the organs 
of animals at the four different times indicated above, the last three 
being from the same locality, shows that it varied slightly : 

1. Eabbits died in 2 days, mice in 1 and 2 days after inoculation. One pig 4 to 5 
nu)nth8 old, which had received subcutaneously the contents of two Pravaz syringes 
of bouillon cultui-e subcutaneously, died in 24 hours. A second pig treated in the 
same way died in 48 hours. 

2. Mice died in 24 hours. 

3. Mice died in 24 hours ; rabbits in 2 to 3 days ; guinea-pigs in 4 to 8 days. 

4. Mice and rabbits died in 24 hours ; guinea-pigs in 2 too days; one pig, which 
had received a syriugefnl of a bouillon culture into each lung, died in 2 to 3 days. 

The lesions in guinea-pigs, rabbits, and mice are, in the main, those 
obtained with the bacteria of our swine plague. The above table indi- 
cates that the bacteria from the last lot were the most virulent, as they 
w^ere fatal to rabbits in 24: hours. 

Through the kindness of Prof. W. H, Welch, of the Johns Hopkins 
University, a culture of the German swine-plague germ was obtained in 
1880, and a second fresh culture in 1890, both from the Berlin Hygienic 
Institute. Both were compared with the American varieties of the 
swine-plague bacteria. While the bacteria in both cultures were iden- 
tical in form and biological characters with the swine-plague bacteria 
of this country, their pathogenic properties varied somewhat, as will 
be seen from the following experiments : 

June 18, 1889. From the original agar tube agar roll-cultures were made, and from 
2 colonies peptone-bouillon cultures prepared. 

June 25. Two rabbits received subcutaneously one-eighth and one-sixteenth cubic 
centimetre, respectively, 2 mice each about one-sixteenth cubic centimetre. 

June 26. One mouse dead this morning. Large, dark spleen, fatty liver. No bac- 
teria detected in cover-glass preparations from blood, spleen, or liver. On the follow- 
ing day a few colonies had appeared in the agar culture from spleen. 

June 27. Second mouse dead. Spleen slightly enlarged, liver fatty. In spleen and 
blood very many swine-plague bacteria, exhibiting the polar stain. 

Neither of the rabbits died. The one which had received one-eighth cubic centi- 
metre had a temperature of 106.4 ° F. on the third day. The temperature of the other 
was not taken. Both were killed 18 days after the inoculatiou. The first rabbitcuu- 
siderably emaciated. On the inoculated thigh an abscess as large as a hen's egg, 
diadiarging from an opening thick pus. The suppuration had extended to the abdo- 
men, vwhere over 6 square inches of the subcutis was infiltrated with pus and firmly 
adheveut to abdominal muscles, In the second rabbit a small abscess as large as a 
Aiwrblfckin iupf-ulated thigh. Spleiisfli considerably enlarged. Feycr's patches swolleu. 



128 

The attenuated condition of these bacteria discouraged any attempts 
to determine their effect upon swine. 

The second culture received in 1890 proved to be a far more virulent 
type, since inoculation of rabbits was invariably fatal within 20 hours. 
These bacteria did not differ therefore in this respect from those 
obtained from outbreaks VII and IX. At the same time their viru- 
lence was still greater, as will appear from the following trials upon 
swine: 

January 9, 1891. Pig No. 435, black male, mixed grade, 4^ months old, received 
enbciitaneonsly into each thigh 2i cubic centimetres of a peptone-bouillon culture, 
or 5 cubic centimetres in all. Dies just 24 hours later. 

Pig No. 437, black and white female, 4J months old, one-half cnbic centimetre of 
the same culture injected into a vein of leg. Animal struggled so that the quantity 
injected may have been more or less than one-half cubic centimetre. Dead in 36 
hours. 

In both animals there was considerable necrosis of the skin and oedema of the sub- 
cutis where the inoculation was made. These animals were not examined until post- 
mortem changes had appeared, owing to other work, so that the autopsy notes are 
omitted. The following two cases are of interest in that the quantity of culture 
liquid injected was smaller. 

February 11. No. 460, black and sandy female, 3^ months old, weight 60 pounds, 
inoculated subcutaneously with I cubic centimetre of a bouillon culture 24 hours old, 
one-half injected into each thigh. 

No. 461, animal of the same kind, inoculated in the same manner with 3 cubic 
centimetres. 

Both were found unable to rise on the following morning and died at 8 p. m., about 
28 hours after inoculation. 

Autopsy early next morning. No. 461 in good condition, deneral blush of skin 
on ventral aspect of bodj' and limbs. Slight reddening of subcutaneous fat. On 
both inoculated thighs the connective tissue reddened and all minute vessels injected. 
On the right the connective tissue has also a glistening (Edematous appearance which 
extends upon abdomen as far as umbilicus. 

Considerable blood extravasation on pericardium and on epicardium along the 
base of the heart, interventricular grooves and left ventricle. Veins on the surface 
of the heart distended. In right side a very dark, soft clot imbedded in thick, tarry 
blood. Lungs normal. Intestines have a uniformly reddened appearance from the 
outside. Stomach about half full of food. Mucosa of fundus hypersemic. Mucosa 
of small intestine normal. In large intestine much dry feces. Mucosa of cjecum and 
colon of a wine-red color. Liver somewhat flabby. The surface has a mottled ap- 
pearance due to the varying hyperajmia of the lobules. In the gall-bladder a firm 
body which almost fills it out and has the appearance of beeswax. The body is 
readily crushed with the fingers. Surrounding this body is a yellowish-white, pasty 
mass. Kidneys hypenemic. 

In cover-glass preparations of blood and kidneys many bacteria exhibiting the 
polar stain ; in liver, only a few. On inclined agar traces from blood, kidney, and 
liver transferred with wire gave rise to a very dense growth of swine-plague liac- 
teria. 

No. 460. From the cut ends of the subcutaneous veins thick, dark blood exudes. 
Skin and subcutis as in No. 461, the vascular injection on the thighs more pro- 
nounced. 

Intestines and stomach appear much reddened from the outside. On the abdominal 
walls and coils of large intestine are little lumps of yellowish-white exudate. A few 
coils of the small intestine where they touch each other show bands of petechia} un- 
der serosa. 



129 

Coiulition of liwirt. ;V3 iu 4(31. TIio ri-rlvt vontral lol)(^ of lungs fasitMiotl to poricar- 
tliiiiu by two old adhesions. Soine8iil>ploiiral iKMOorrliai^os on principal lobes. .Slinlit 
ronjrbeuiug of plonra ovor the vontral iialf of both hiiigs. Paroncliynia noniial. 

Mucosa of fundus of stomach ovor an area G inclios in diaiiiotor uuicli rcddciu-d, 
the hypcra'uiia oxtending to subinncosa. Small iutostiiu) contains occasional patcibcs 
of congostod mucosa. In the largo intostino bypera-mia slight compared with 4<)1. 
Kidneys and liver as in 4G1. 

In the blood many swine-plague bacteria. Cultures therefrom aiul fiom kidneys 
confirmatory. 

It should be noted that wliile these German swine-plagiie bacteria 
were fatal after .subcutaiicoiis inocnlatiou, the only cultures of the 
American variety which killed swine after su(;h inoculation were from 
outbreaks I, J I, and IX. Even the bacteria from the latter outbreak, 
virulent as they were, failed in this respect iu all but one case.* 

Additional investigations concernino- iSchweineKeuche were made by 
Bleisch and Fiedelerf in 1888-'89. The disease appeared in Septetuber 
on a dairy farm, evidently introduced by recently luirchased animals. 
It spread amoug the swine in several different stables, even among 
those which did not come in direct contact with the pur(;hased animals, 
but were simply placed in the i)ens evacuated by the latter. Even after 
the disinfection of two stables the animals put into them contracted the 
disease. The investigations were continued nntil February, 1889, and 
in all fifty-two animals were examined. The disease had been compar- 
atively mild and chronic ; none of the infected died, and the lesions were 
observed In the slaughtered animals. 

During life the symptoms consisted of coughing, which increased in 
severity when fresh air entered the stables, difficult breathing, loss of 
appetite, and emaciation. The temperature fluctuated between 102° 
and lOS'^ F. The lesions observed in the bntchered animals were in 
the main limited to the thoracic organs. The anterior (or cephalic) 
lobes were involved in grayish-red hepatization, which iu more ad- 
vanced cases invaded the middle and posterior (ventral and principal) 
lobes, the latter only in isolated regions. The bronchus always forjiied 
the central point of the hepatization. As the disease progressed par. 
tial caseation of the hepatized tissue and of the bronchial glands took 
place. The caseous masses did not contain tubercle bacilli. Pleuritis 
was found only iu advanced cases, pericarditis still more rarely. 

The authors found in practically all cases bacteria, which they 
identify with the bacteria of Schiceineseuche or swine plague. They 
were obtained both by inoculating rabbits and fowls with particles of 
lung tissue, and more rarely on plate cultures from the lung tissue 
directly. The bacteria obtained are so far as the description goes 
identical morphologically with the bacteria found by Lofifler, Schiitz, 
and others. Their effect on rabbits differs iu some respects from the 
disease produced by the swine-plague bacteria proper. The disease 

* Sec p. 74. 

t Zeitschrift f. Hygiene, vi (1889), S. 401-452. > 
1614 9 



130 

may last from 2 to 13 days. An examination of the text shows 
that some rabbits lived longer, one 27 days. At the point of inocula- 
tion there is more or less subcutaneous purulent infiltration with puru- 
lent lymphangitis. The liver contained in many cases embolic foci, 
which are described (p. 406) as partly branched, partly yellowish-white 
spots found on the surface and on section, and consisting of a pasty 
mass. A careful examination of the text fails to convince me that 
these embolic foci had any connection with the disease. Their descrip- 
tion suggests very strongly cysts of coccidium oviforme in various stages 
of enlargement. Thus a rabbit which died in 24 hours from an intratho- 
racic inoculation of these swine- plague bacteria showed at tlie autopsy 
"the liver very large, the surface studded with numerous, projecting, 
yellowish nodules as large as pease, similarly the cut surface." The 
coccidia, if such the3^ may have been, are easily overlooked in cover- 
glass preparations, for the method of preparation and staining de- 
stroys them pretty thoroughly. Moreover, these embolic foci do not, 
according to their report, appear with any regularity in the inoculated 
animals. 

Another point to be noted in the lesions of inoculated rabbits is the 
absence of exudative peritonitis or i^leuritis, which is a very constant 
lesion in rabbits inoculated with the American races of swine plague 
bacteria when they live more than two days after inoculation. 

While swine- plague bacteria have little or no effect upon fowls unless 
large doses are injected into the muscles, the variety under discussion 
was virulent enough to prove fatal to almost all fowls inoculated. 
Death occurred from one day to several weeks after inoculation. In one 
of these " liver emb oli " were observed. One pig which had received a 
Pravaz syringe full of bouillon culture of these bacteria died in ten 
hours. The lesions observed were pleuritic effusion, hepatization of 
almost the whole of the right lung. In the left there were isolated 
masses of hepatization. A second pig which received a subcutaneous 
injection had a slightly elevated temperature for several days, but it 
recovered subsequently. 

In several diseased pigs there were found ulcers on the surface of tlie 
body. In one a series of caseous cysts, starting from the castration 
wound and extending along the subperitoneal tissue as far as the um- 
bilicus, was observed. The relation of these lesions to the disease is, 
of course, not determinable. 

The authors, after having determined the cause of the disease, en- 
deavored to find out how the bacteria are transmitted from one animal 
to another. The swine examined belonged to one farm and were fed 
chiefly with sour whey. In this whey, taken from the troughs, bacteria 
probably identical with the disease germs were found on two different 
occasions. Further investigation revealed the fact that while fresli 
milk is not a good soil for these bacteria, sour whey is very favorable 
to their multiplication. The authors therefore explain the transmissioi) 



131 

of the disease by assuming that in the common feeding trough the bac- 
teria are mixed with the milli^.* Some of this accidentally getting into 
the air passages during feeding introduces the disease germs. 

This brief review of the investigations indicates that while the bac- 
teria found by Bleisch and Fiedeler are not hog-cholera bacilli and in 
general the same as swine-plague bacteria, there are some minor but 
constant differences to which attention has been called. It is a curious 
fact that these bacteria were attenuated with reference to rabbits, but 
still latal to fowls. Towards the varieties described in this report, the 
fowl, among smaller animals, manifested the greatest and the rabbit 
the least ])ower of resistance. It is not improbable that attenuation, as 
we understand the term, may imply a decrease of virulence as to one 
species and at the same time an increase as to others. It is not unreason- 
able to assume that a variety of swine-plague bacteria, apparently atten- 
uated so far as rabbits are concerned, may still i)Ossess virulent proper- 
ties as regards more refractory animals. The properties which make it 
feeble to rabbits ami virulent to swine, for instance, nmy prove different 
from each other. It is only by such assumption that we can understand 
the action of swine-j^lague bacteria from outbreak I and II, which, 
though attenuated with reference to rabbits, were fatal to swine. 

A very interesting communication on the subject of swine diseases 
in Germany was recently made by F. Peters, of Schwerin.t During 
the winter of 1887-88 this author examined cases of a disease among 
swine which strongly suggests hog cholera. The disease is described 
in brief as follows : 

Soon after the sucking period is completed, the young i)igs lose their 
desire for food and become emaciated. Cough, increased respiration, 
paleness of the mucous membranes, and diarrhea are also observed. 
Towards the fatal close of the disease, which lasts from 3 to 6 weeks, 
the skin of the ears, the neck, and chest becomes reddened. The greater 
number of those attacked die. In four cases, the large intestine only 
was affected. The description given corresponds closel.y with the vari- 
ous forms of necrosis, softening and induration commonly called ulcers 
in hog cholera for the sake of simplicity. In a fifth case, in addition to 
the intestinal changes, there were found recent hepatization of the left 
lung and exudative pleuritis. 

The author made some bacteriological examinations, but they were 
not thorough enough to furnish any reliable information concerning the 
character of the bacteria found. While he maintains that they are 
swine-plague bacteria the description he gives would equally apply, as far 
as it goes, to hog-cholera bacilli. As the territory of Schwerin is not 
very far from Denmark, the scene of swine pest (hog cholera) during 
1887 and since that time, it is not improbable that this region i.s slowly 
being invaded by two diseases, the Schweineseuche, or swine plague, 

* The Americao varieties of swine-plague bacteria refuse to grow iu acid lueclia, 
t Pi© Scliweineseuche. Arcliiv f. Thierheilkuudo, 1890, xvi, S. 64, 



132 

found by Scbiitz iu 1885, and the swiiie pest, or hogcliolera, first noticed 
in Sweden and Denmark in 1887.* This possibility has been suggested 
recently by Bunzl-Federn t in an article devoted to swine-plague and 
closely related bacteria. The problem of infections swine diseases 
would then enter the phase iu which the investigations of this Bureau 
found it as far back as 1886 in this country, in which a mixture of two 
diseases is encountered more frequently than either disease by itself. 

In this summary some articles of minor importance have remained 
unnoticed. Likewise the observations of Eoloff | on caseous changes 
in the intestines of young pigs have been passed by because they give 
us no information as to the nature of the bacteria involved in the 
disease. The views of some that his cases were swine plague, of others 
that they may have been hog cholera, are purely hypothetical. 

* See Special Report on Hog Cholera, 1889, p. 181. 
t Archiv f. Hygiene, xir, 1891, S. 198. 

tDie Schwindsncht, fettige Degeneration, Scrophuloso unci Tuberkulose bei 
Schweiueu. Berlin, 1875. 



SOME PRACTICAL OBSERVATIONS ON THE PREVENTION OP 

SWINE PLAGUE. 

1. CONDITIONS WHICH MAY FAVOR AND OPPOSE OUTBREAKS OF SWINE 

DISEASE. 

Tlie factors wbicli enter into tlio production of outbreaks of swine 
plague may be divided for convenience into two classes, those pertaining 
to tlie animal itself, and whicli make it more or less susceptible or insus- 
ceptible to the specific bacteria, and those which relate to the bacteria. 

The conditions which make animals more susceptible to infection are 
as varied as the conditions which reduce their vitality. The importance 
of rearing and keeping animals in such a manner as to produce and 
maintain a healthy action of the various functions of the body has not 
been insisted upon with as much emphasis as it deserves, owing to the 
somewhat overshadowing. intluence which the study of pathogenic 
bacteria has exerted upon all minds. It is evident, however, that vet- 
erinary hygiene has much to do with the decline of large epizootics, not 
only by keeping away the germs of disease, but bj' enabling the animal 
body to resist their attacks. Of those conditions of swine which invite 
disease very little is as yet positively known, and we simply call atten- 
tion to a few to arouse the interest of those who are in position to make 
observations. 

There have been indications during the course of experiments at the 
Bureau Station that the breed may have some influence in predisposing 
to infection. As an illustration we may cite an experiment in vaccina- 
tion of swine against hog cholera carried on at the Station in 1889-90.* 
The vaccination, which consisted in subcutaneous inoculation of culture 
licpiid, seems to have had no effect ; for, wlien the tinn^. for exposure came, 
practically all pigs from one lot succumbed and all from another lot 
survived. The latter were Essex grades reared in pens; the former, 
grades of mixed Jersey Reds and Chester Whiles not raised in pens. 
While it is imi)0ssible to give any facts as to the relative resistance of 
different breeds to swine diseases, it is a subject which should receive 
the due consideration of swine-breeders, especially in those States 
where swine diseases are more or less stationary. 

Age is another important element. We have found a decided differ- 
ence in the susceptibility to both hog cholera and swine plague in favor 
of older swine. This element of age is familiar to all with reference to 



' Report of the Sccret:iry of Agriculture for 1890, p. 110. 



133 



134 

certain human maladies, such as scarlet fever, measles, diphtheria, and 
some other diseases which preferably attack the young. 

Feeding- is perhaps the most important factor in predisposing swine 
to disease. The assimilation of large quantities of food and its con- 
version into fat seems to be the one essential function of swine. This 
goes on to such a degree as to lead to pathological conditions after a time. 
IvTot only the ingestion of large quantities of food, but of one kind for a 
long time, is in itself opposed to the habits of such omnivorous animals. 
Besides overfeeding upon one kind of food we have the uncleanly sur- 
roundings in which swine are apt to be kept contributing materially to 
a reduction of vitality. 

In addition to the unhealthfiil modes of existence to which swine are 
subjected, and partly springing from them, are certain pathological con- 
ditions induced by parasites of different kinds. The life history of some 
of the more important parasites infesting swine is still to be elucidated. 
As a rule, we have found in our post-mortem examinations a larger 
number and variety of internal parasites in those herds which have 
been allowed to run freely than in those brought up in pens. The op- 
portunities for infection seem to be much greater in the former case 
than in the latter. 

As to the damage done by parasites it is difficult to form an accurate 
estimate from ordinary observation. Obvious damage may be done in 
the air passages by lung worms [strongyhis paradoxus) and in the small 
intestine by ascaris and echinorhi/nchus. The lung worms may be 
met with in all seasons of the year in swine up to 3 mouths old. They 
invariably inhabit the terminal portion of the two large bronchi of the 
principal lobes. Here there is generally a partial or total occlusion 
of the bronchus for 1 or 2 inches from the caudal border of the lobe, 
due to the lung worms and the enveloping mucus. In some cases the 
occlusion is followed by collapse and broncho-pneumonia of the lobes 
supplied by the bronchus and its branches. The hepatized lung tissue 
assumes a bright or pale red color. When the lung worms are very 
abundant larger branches of the same bronchus become filled with 
these parasites and the broncho-pneumonia may extend over a greater 
l^ortion of the principal lobes. That lungs in this condition are more 
suscepti()le to the invasion of swine-plague bacteria will be generally 
admitted. The bronchitis begun where the lung worms mature may 
extend after a time into the other air tubes. In outbreaks YII and 
VIII lung worms were found in almost every animal examined. 

Another question arises with reference to lung worms as the possible 
bearers of the bacteria into the lungs. This will not be answered until 
more is known of the life history of these [)arasites. Meanwhile the 
evidence would hardly support the opinion that they may introduce the 
virus. The i)ueumonia usually begins in the small ventral lobes and 
travels from them while the lung worms begin their injurious work in 
the j)rincipal lobes farthest removed from the ventral lobes. All that 



135 

can be said is tliat they may make the lungs more susceptible to the 
disease. 

In the intestines ascarides are not infrequently found extending- into 
the common bile duct from the duodenum. Some even enter the gall- 
bladder, while others imbed themselves iu the ducts coming from the 
various lobes of the liver and completely obstruct the flow of bile. The 
echhiorhynchus is well known as attaching itself to the mucous mem- 
brane of the small intestine, and producing ulcerous depressions simu- 
lating those of hog cholera. 

That there may be other predisposing causes at certain seasons of 
the year, such as obscure malarial diseases due to protozoa, the inva- 
sion of the muscular system by psorospermia, trichina', etc., ueed simply 
to be mentioned, since no positive evidence is at hand. 

The important factor in the production of swine plague (and hog 
cholera as well) bearing on the bacteria is their virulence. VVe have 
seen in the chapter on the pathogenic action of swine-plague bacteria 
that their virulence or disease-producing power is subject to consider- 
able variation, and that they may be very virulent as obtained from one 
outbreak and much less so from another. It may be laid down as a 
general rule that the more virulent the bacteria the more severe the 
resulting epizootic, and the greater the mortality. While a more attenu- 
ated variety of bacteria may spare the older and more hardy animals 
of a herd, these will succumb to a more virulent variety. Just here 
the facts presented under the preceding head show their importance. 
Attenuated or weaker varieties of swine plague ma^^ attack the young 
and the badly kept swine, those infested with parasites and those of 
poorer breeds, while the stronger may not become diseased. This may 
explain also why some herds of swine are destroyed and neighboring 
ones escape, although both may have had the same opportunities of 
infection. 

The appearance of an epizootic depends thus upon the condition of 
the herd and the relative virulence of the bacteria. While there are 
bacteria whose virulence is sufficient to sweep away every obstacle, we 
are convinced also that much disease due to attenuated bacteria could 
be counteracted by a more hygienic breeding and rearing of swine. 

2. THE DISTRIBUTION AND TRANSMISSION OF SWINE-rLA(;UE BAC- 
TERIA. 

We have seen in preceding pages that besides the particular herd in 
which swine plague exists as an epizor>tic, bacteria not distinguishable 
from those of swine plague are found widely distributed in the air pas- 
sages of healthy swine, and of other domesticated animals, such as 
cattle, dogs, and cats. Are these bacteria capable of producing disease 
in swine at any time and therefore a continual source of danger, or are 
they harmless ? This question can not be answered definitely in the 
present state of knowledge on this subject. As a rule, the bacteria 



136 

found in liealthy animals belong to more or less attenuated varieties and 
are most likely incapable of producing disease excepting when the con- 
dition of the animals is very poor. Sporadic disease in such debilitated 
animals is not contagious and does not spread to other animals of the 
herd unless all are in equally reduced condition. It may happen, how- 
ever, that such swine plague bacteria, which live in the air passages of 
older swine as survivals of former exposure and disease, may become 
dangerous to young pigs. Of this possibility outbreak VIII may serve 
as an illustration. The litter of young pigs died of swine plague 
caused by a considerably attenuated variety of bacteria, such as may 
be found in apparently healthy swine of greater age. It should also 
be remembered that even older swine, which have been through the 
fattening process and are, commercially speaking, in the best condition, 
are really in an abnormal or a pathological state, and, therefore, may 
be more or less susceptible to infection. 

We have shown that there are herds of swine from certain farms en- 
tirely free from pathogenic bacteria, and the question arises. What is the 
source of those swine plague-like bacteria found in the upper air pas- 
sages of many herds? I am inclined to think that they are transmitted 
from older swine to younger ones, producing disease only under aggra- 
vated conditions in isolated cases, which disease does not spread to 
other animals. 

When we come to the more virulent varieties, those for example, 
which destroy rabbits within 16 hours after inoculation, the case is 
entirely different. Their presence is probably never manifested ex- 
cepting by disease, and it is against the introduction of these bacteria 
that the swine-breeder must protect himself. Such bacteria always 
come from some outbreak of disease directly or indirectly. Let us con- 
sider brieHy through what agencies such bacteria may be introduced 
into a herd. 

In the report on hog cholera and in the present volume it was pointed 
out that swine-plague bacteria are far less hardy than hog- cholera 
bacilli.* The former perish rapidly in water and in liquids unsuited to 
their multiplication. They survive drying for a few days only. In gen- 
eral, they speedilj^ disappear after they have left the body of diseased 
swine, and it is highly doubtful whether they would survive a month in 
the soil or in pens. Such agencies as streams, manure, etc., which maj^ 
distribute hog-cholera bacilli over considerable distances are of re- 
stricted importance in swine plague. The chief danger lies in contact 
with diseased or infected swine. Intermediate carriers of infection can 
only act for a short time, while swine may harbor disease germs for 
months in localized inflammations, such as abscesses under the skin and 
in the joints, and it is possible that they may vegetate on the mucous 
membranes of the air passages much longer. 

* See table, p. 92. 



137 

Swine miLst thus be regarded as the chief voliiclc of infection. This 
may be conveyed directly from diseased to iiealthy animals; it may bo 
conveyed by those Miiich have passed through the disease, and hence 
by older to younger swine. It is safe to assume that any swine which 
have at any time been exposed to swine plague (or hog cholera) are 
liable to convey the disease, because we do not know when the specific 
disease germs leave the body. 

Other sources of danger are railroads leaving fresh manure in differ- 
ent places, tlie vicinity of slaughter-houses, rendering establishments, 
or any places where the viscera of swine may be scattered or where 
numbers of living swine are temporarily housed. If we bear in mind 
the wide distribution of infectious swine diseases it is easy to believe 
that in any large herd of swine collected from different localities there 
are always some diseased or infected. It is essential, therefore, in 
guarding against disease, to look with suspicion upon all swine the 
history of which is not known to some extent at least. 

There is a practice current in some parts of the country, and well 
illustrated by the history of outbreak IX, of gathering together herds 
of young pigs from various localities through the intervention of deal- 
ers. In regions where swine diseases are prevalent much of the time, 
and where the virus never dies out, this is a specially dangerous practice. 
While swine may not be visibly diseased, or may simply appear some- 
what unthrifty, they still may carry the seeds of a virulent outbreak 
within them which need a little time to gain the required momentum. 
The mild character of a disease in anyone animal is no evidence of the 
character of the germ. For this mildness may be due to a very viru- 
lent germ acting upon a highly insusceptible animal and causing a 
more prolonged chronic disease. In fact, these partly insusceptible ani- 
mals are the most likely to appear in the markets because they are the 
remnants of herds destroyed by disease. We have frequently been able 
to demonstrate by exi)erimental inoculations the general accuracy of 
these statements. Thus bacteria obtained from inoculated cases which 
had assumed a more chronic course had not lost any of their virulence. 
In ex[)eriments bearing on Aaccination we have been able to increase 
the insusceptibility of rabbits aud guinea-pigs so that virulent bacteria 
l)roduced only a mild form of the disease, i)rolouged from days to weeks 
and even months. Yet the bacteria cultivated from such cases and in 
jected into animals not vaccinated showed no loss of virulence. Again, 
we have found swine-plague bacteria in apparently healthy swine inocu- 
lated two months previously, and in case of hog cholera we have found 
the bacilli in the organs of swine G to 7 months after api)arently un- 
successful inoculations. These bacteria possessed the original viru- 
lence. 

The question has frequently arisen in the course of these investiga- 
tions whether the bacteria are ever introduced into herds in the food. 
This involves another question, whether hog-cholera or swine-plague 



138 

bacteria do exist indepeudeutly of diseased or healthy animals. As to 
both kinds of disease germs there is no evidence that they live outside 
of the animal organism, except temporarily, and that if the food happens 
to be infected the infection has come from animals directly or indirectly, 
and that it is simply a question of time whether such infection is still in 
a living condition or not. Food, however, may be infected with other 
pathogenic bacteria which may become dangerous in producing second- 
ary and i)erhaps fatal lesions in animals already diseased. This applies 
more directly to the swill food which is used by many in the vicinity of 
large cities and which is composed of such miscellaneous material partly 
in a condition of fermentation and decomposition that the presence of 
disease germs may be considered probable at any time. In outbreak 
IX, in which swill food was mainly used, the bacilli of malignant a?dema 
were obtained from some cases and very likely added to the fatality of 
the outbreak. 

3. THE RELATION OF HOG CHOLERA TO SWINE PLAGUE.* 

Throughout this report frequent reference has been made to hog 
cholera because many outbreaks studied during the past five or six 
years were mixtures of both diseases, and it is therefore difQcult to sep- 
arate them in order to estimate correctly the damage done by each. 
We have encountered a small number of outbreaks, of which some were 
due to hog cholera, others to swine plague, but the majority were the 
result of a mixed infection. 

The outbreaks of hog cholera not complicated with swine plague were 
generally of a virulent type. When both diseases showed themselves, _ 
neither was, as a rule, of any great virulence. To explain the frequent 
intermingling of these diseases we must refer to the bacteriological re- 
sults of the past few years. Besides the virulent varieties of hog-chol- 
era bacilli, which produce a characteristic fatal disease in rabbits after 
subcutaneous inoculation of exceedingly minute doses, we have encoun- 
tered about half a dozen varieties whose virulence was much diminished. 
The diminishing pathogenic power is shown by the absence of a fatal 
disease after subcutaneous inoculation of rabbits, and even small quan- 
tities of culture liquid injected into the circulation may produce only a 
mild disease. In onet there seemed to be no virulence left, and it 
becomes questionable whether such bacilli can be regarded as hog- 
cholera bacilli at all. The attenuated bacilli have likewise very little 
or no effect on swine. 

Parallel to this diminishing scale of virulence of hog-cholera bacilli, 
we have a similar scale among swine-plague bacteria repeatedlj^ set 
forth in the preceding pages. On the one hand, some varieties will 
destroy rabbits within 10 hours after inoculation of the minutest trace 
of culture material into the skin ; on the other there are varieties 
whichbarely destroy rabbits after large doses have been injected directly 

* See also pp. 102-108. t Bacillus y, outbreak IX, p. 78. 



139 

into the circulating blood. All of these varieties have been obtained 
from the internal organs of diseased swine, and hence even the very at- 
tenuated ones may have had some share in the disease. 

If we picture to ourselves a wide distribution of these several varie- 
ties of hog-cholera and swine-plague bacteria in the bodies of diseased 
and of partly recovered swine, and, in case of swine-plague varieties, 
in the air passages of healthy animals, it is not difficult to understand 
why there are so many mixed outbreaks. The practice already alluded 
to, of purchasing pigs from many herds and localities and bringing tliem 
together to be fattened as one herd, is the most successful method of 
bringing various grades of pathogenic bacteria together and of pro- 
ducing a mingling of two diseases. These mixed outbreaks may de- 
velop in other ways also. The disease may begin as hog cholera and 
become subsequently complicated Mitli swine plague or the reverse 
may be true ; the disease may begin as swine plague, and become com- 
l)licated with hog cholera. In either case the most virulent variety 
will i)robably start the disease, and anj' attenuated hog-cholera or swine- 
])higue bacteria, which are latent in some of the animals of the herd, 
or have not yet been killed out of the soil, aud the surroundings from 
a former outbreak may start into activity and thus produce a more 
fatal mixed disease. It is evident that such secondary attacks of atten- 
uated bacteria would not take place if the animals had not been weak- 
ened by the primary disease. This may be the only way in which the 
great majority of the swine-plague bacteria in the air passages of 
healthy animals can exert any i)athogenic effect whatever. It is like- 
wise difficult to understand how attenuated hog-cholera bacilli can act 
without assistance from swine plague. These statements may be illus- 
trated by referring to the investigations. Thus in outbreak IV the dis- 
ease was evidently swine plague at first, and complicated with hog- 
cholera later. For the hog-cholera bacilli were only observed in the later 
cases. It should Ukewise be borne in mind that in swine plague some 
cases are usually of a more chronic type. The disease lasts some time 
and is associated with caseous changes in the lungs. Any hog-cholera 
bacilli have thus abundant opportunity to enter the weakened organism 
and appear after death in cultures from the internal organs. For the same 
reason hog-cholera outbreaks characterized by very feeble pathogenic 
activity of the hogcholera bacilli, and hence of a more prolonged dura- 
tion and chronic character, are usually complicated with swine plague, 
because the latter, even though of a feeble activity, has been able to in- 
vade the weakened organism and has had time to do so. In virulent 
outbreaks of either disease death may ensue so rapidly that no invasion 
of the other disease takes place. These statements presuppose, of 
course, that both kinds of bacteria exist in the surrouiulings of the herd. 

The appearance of mixed outbreaks due to bacteria brought b}' dif- 
ferent herds is suggested by outbreak VII. Even after a very thorough 
examination of Xos. 1 and 2 no hog-cholera bacilli could be found. In 
the subsequent cases in which they were present, they were readily de- 



140 



tectcd 111 the various organs examined. Moreover there was quite a 
ditfereuce observable in the lesions of the various cases eorresnondiu.- 
aiore or less closely to the nature of the bacteria found. The supposi^ 
tion already presented in regard to this outbreak was that the ho-chol- 
era bacilli were either present in the locality, into which the pigs were 
brought or were carried by some oue or more pigs in the herd 

Hog cholera aud swine plague thus mutually assist one another to 
produce those feebly infectious, chronic diseases which are common at 
all seasons of the year, and it is not unreasonable to suppose that from 
such apparently insignificant diseases large epizootics are developed 
which by a gradual return of virulence in the bacteria, and under sli o-ht 
provocations of forced feeding, cold, or other debilitating intiuen^.es 
on the part of their victims, burst forth at certain seasons^of the year 
with unexpected violence.* 

This condition of things refers more particularly to localities where 
swme-raising has been conducted on a large scale, where these dis- 
eases never actually die out, and where consequently the specific 
bacteria are always on hand. In those regions which are being invaded 
by tuese^plagues anew the latter may smolder for several years by 
reason of the introduction of attenuated varieties before they break 
out as genuine epizootics. ' 

There are no facts at hand to indicate any difference in the distribu- 
tion of these two plagues. The localities where either one or both 
plagues have been determined by bacteriological investigations may 
be tabulated as follows: * may 



Locality. 



Character of plague. 



By the Bureau of Animal Industrv 

DiHtiifl nf rv.1„.v.i.;.. !' _ 



Mar3'lau(], various outbreaks 1885-'90 Jiog ctiolora. 

Virginia, various outbreaks 1885-'90 --.Uo 

Nebraska, 188G --"o 

Illinois (Geneseo), July, 1886 .". | ■ - . . do 

nimois (Soilorus), September, issh'.'.'.'.'.'." " 



Iowa, December, 1886 

Iowa (Mason City), November, 1888' 

^ew Jersey (Jolinsonbiiifih). October 1887 
-New Jersey (I'leasantvillo). Julv 1890 

Missouri (Cliillicotlie), 1890-'91 -' 

Nebraska (188G-'88), by EiUings.. 

Maryland (Baltimore), by Welch and Clement* 

bouth Carolina, by Bolton 

Illinois, byl3urrill 

Massachusetts (near Boston)Vb'y il." A.' Jeffries! 



Hog cholera. 



*(?) 
t(?) 

Hog cholera. 

..do 

.- do 

...do 



Swiue plague. 
Do. 
Do. 

Swine plague. 
Do. 
Do. 
Do. 

Swine plague. 
Do. 

o • *■' 

bwine plague. 

Swine plague. 
I Do. 

Ivtr'T '"f '"''"" t *'^i^'-««'-"'i^«cence of apparently enfeebled virus is outbr^ 
I^ re erred to above During February and March swine plague fron. a neighborL: 
farm became nnngled with hog cholera in an infected pen on the Station in which thrs 

slight seventy so far as hog cholera lesions were concerned. Gradually towards 
spnug, anunals placed in this pen died rapidly of hon.orrhagic hog cholera The! 
was no evidence of the introduction of another bacillus, nor were any^hangrdete "ed 
as regards the bacteria in cultures or in tlie inoculated rabbits 



141 

4. THE RELATION OF SWINK PEAGUl-: TO DISEASES OF OT?FER DOMES- 
TICATED ANIMALS. 

The question whether the diflereiit species of tloinestieated animals 
on a farm may take from or transmit to swine the disease which we 
liave been considering^ is of very great importance in view of the chanj?- 
iiii;- ctuiditions of live-stock interests which are i;oin!jf on in different 
directions in varions parts of onr country. 

The problem may be stated as follows : Has the bringing together 
of different species of animals for the purposes of feeding, etc., on the 
same ground, a tendency to increase disease in one or the other species ? 
Will swine take swine plague from cattle and will tiiey transmit it to 
sheei) and horses, for exami)le, or is the reverse ever observed ? 

Investigations and observations during the past b'i years lend some 
color to such possibilities, and it becomes necessary at least to call at- 
tention to those engaged in raising and keeping farm animals to what 
has been determined in this direction, and to arouse their interest in 
the investigation of outbreaks of swine i)lague, especially as regards 
the immediate causes. 

In the summer of 3878 there appeared in three royal game preserves, 
in the vicinitv of Munich in Bavaria, a very fatal epizootic among the 
wild boars and deer, of which 234 boars and 153 deer perished.* It 
w^asalso noticed that even after the plague in the parks had apparently' 
died out, disease among cattle in the neighborhood appeared, and this, 
according to the observations of veterinarians, was identical with the 
disease observed among the game in the parks. 

The disease was very acute, lasting from 12 to 30 hours in the major- 
ity of cases. In those in which pneumonia and pleuritis were present the 
disease may have lasted 5 or days. The chief lesions among the latter 
were croupous pneumonia, pleuritis, pericarditis, and mediastinitis. 
In cattle the disease appeared in two forms. In one a swelling was 
observed on the head, the face, the neck, or in the tongue, which as- 
sumed enormous proportions inG to 12 hours and led to suftbcation. The 
swelling was due to serous or serous and hemorrhagic infiltration. In 
the other form, in addition to the pneumonia, pleuritis, and pericarditis 
observed in the game, there was always present a severe hemorrhagic 
inflammation of the small intestine. Bollinger called these forms exan. 
thematic and pectoral, respectively. At this time bacteriological meth- 
ods were still undeveloped, and nothing is known of the nature of the 
bacteria causing this outbreak save the fact that they were not anthrax 
bacilli. A number of inoculations were made upon various animals, 
which testify- to the extreme virulence of the specific bacteria. 

Rabbits died 6 to 8 hours, sheep and goats 30 to 36 hours after inocu- 
lation. Two old horses died after subcutaneous inoculation with blood 
from cattle in a very short time. A young steer, li years old, was fed 

• Bollinger. Uber eiue neue Wild- unci Riaderseache. Miinchen, 1878. 



142 

with a tbimbleful of the intestinal contents of a calf which had suc- 
cumbed to an enormous swelling-. The steer died in 54 hours with 
pneumonia and i)leuritis. A pig inoculated subcutaneously over the 
left shoulder with a few drops of blood died in 22 hours. Besides an 
extensive erysipelatous swelling- starting from the point of inoculation 
there was beginning fibrinous pleuritis. 

The disease reappeared in the following years, either sporadically or 
in restricted outbreaks. In 1879 and 1880 it was observed among 
domesticated animals alone ; in 1881 among the animals in the game 
preserves. In 1885 Kitt* published some investigations which were 
destined to throw more light upon this new plague. With blood from 
an outbreak among cattle resembling the epizootic described by Bollin- 
ger, Kitt made some inoculations upon small animals. Of mice, rab- 
bits, guinea-pigs, and one pigeon inoculated, the mice and rabbits died 
within 24 to 36 hours, the pigeon in 36 hours. The guinea-pigs were 
not afiected. Lesions were in general absent. The blood contained 
large numbers of bacteria. Subsequently the spleeus of an ox, a young 
pig (of which eight had died), and a horse which had succumbed in the 
same locality, showed on microscopic examination the same bacteria, 
whose virulence tested on rabbits was likewise the same. In a cow in- 
oculated subcutaneously over the left shoulder an extensive inflamma- 
tory cedema of the inoculated shoulder appeared, which extended over 
the entire left limb. The swelling later became converted into an 
abscess, but the animal did not die. 

Of special interest is the subcutaneous inoculation of a pig with a 
minimum quantity of mouse's blood. From the place of inoculation on 
the right thigh a bluish discoloration of the skin spread over the whole 
body in spots and patches, while there was considerable swelling at the 
place of inoculation. The pig was dead in 24 hours. The autopsj' re- 
vealed, in addition to the lesions mentioned, exudative pleuritis and 
peritonitis, congestion of the mucous membrane of the upper air pas- 
sages and of the stomach. A goat inoculated subcutaneously in the 
same manner was afflicted with extensive local inflammatory oedema and 
died within 2 days. A horse inoculated subcutaneously in the neck 
with a suspension from an agar culture, derived originally^ from the 
mouse, died within 1^ days with extensive local reaction, fluid blood, 
ecchymoses on heart, pleuritis and pericarditis, and beginning inflam- 
mation of the mucosa of the stomach. 

The bacteria found by Kitt have a marked resemblance to swine- 
Xdague bacteria, and their pathogenic effect on pigs and smaller animals 
is identical with that of very virulent swine-plague bacteria. Kitt 
states that they grew upon boiled potato as grayish-yellow colonies, 
whereas swine-plague bacteria do not produce any visible growth. An 

* Ueber eine experimentelle, der Rinderseuche (Bollinger) ahnliche Infectionskrank- 
heit. Sitzungsbericbte der Gesellscbaft f, Morphologie und Phyeiologie in Mi^nchen, 
J^ 1885, S. X40-1G8. 



143 

exam i nation of the text leads us, however, to believe that he inoeulated 
potatoes directly with blood. Those who have made many cultures 
of these bacteria have undoubtedly realized how very richly cultures 
have gTowu to which a little blood was transferred from the auimal 
under examiuation. Hence the potato growths were likely due to the 
presence of blood. The further statement that, after an examination of 
Kitt's cultures, Schiitz considered these bacteriai different from those of 
Schwemeseuche (swine plague) because the latter did not kill pigeons is 
worth nothing, because the diftereuce is simply a matter of virulence. The 
great difference among swine-plague bacteria themselves as regards this 
very point we have repeatedly pointed out. 

A disease probably identical with the foregoing was described by 
Oreste and Armanui,* as occurring among herds of young buffaloes in 
Italy. The disease appears very suddenly, and the animals attacked 
may die in from 12 to 24 hours. The symptoms are high temperature, 
rapid and feeble pnlse, discharge of mucus from nose and mouth, asso 
ciated with a local swelling on the head and face which leads to suflb- 
cation. The lesions observed after death are few and inconstant, a 
hemorrhagic indammation of the small intestine being frequeiitly ob- 
served. The specific bacteria seem to be identical morphologically with 
swine-plague bacteria. The disease can be reproduced in young buffa- 
loes by inoculation of cultures. It was similarly produced in a colt, a 
cow, a sheep, and in mice, rabbits, guinea-pigs, pigeons, and fowls. 
Death ensued in all animals in from 1 to 3 days. Of two young pigs 
inoculated one died, the other survived. 

In France, Galtiert has found pneu mo-enteritis of swine associated 
\vith a similiar disease in sheep which came in contact with them. 
While there is much in favor of his assumption that the infection passed 
from the swine to the sheep, the description of the specific bacteria and 
of the methods of inoculation are not sufficiently complete and thorough 
to bring conviction as to the transmission, or furnish any definite in- 
formation concernin g the nature of the bacteria found. A few sugges- 
tions thrown out here and there are sufficient, 1 think, to permit us to 
exclude hog-cholera bacilli and regard them as belonging to the group 
under consideration. 

These various investigations are of great importance in showing that 
some infectious diseases may either attack several species of domesti- 
cated animals at the same time, or be inoculable from one species to 
another. What is of special significance in the first two investigations 
is the extreme virulence of the bacteria. The same may be said of the 
Italian buffalo disease. 

There is another class of infectious diseases, due to bacteria of the 

* Atti del E. iBtituto d' incoraggiamento alle scienze natural!, etc., 1887. For a 
brief account, see also Journal de Mddecine V^t^rinaire, 1887, p, 585, and Banuiga^'^ 
teu's Jaliresbericht for 1887, S. 124. 

t Journal de MfSd. Y6t., 1889, passim, 



144 

same group, which produce specific diseases amoug certain species ot 
domesticated animals, but which diseases are not known to be com- 
municable to other species. Among these are fowl cholera, rabbit septi- 
caemia, and a peculiar form of pleuropneumonia in cattle, which Poels 
has called " septic pleuropneumonia." During the past 3 or 4 years, 
the writer has examined in the laboratory of the Bureau of Animal In- 
dustry a small number of lungs from cattle affected with pneumonia 
from which bacteria practically identical with swine-plague bacteria 
were isolated. A description and discussion of these forms of pneu- 
monia in cattle will be reserved for a future report. 

There is thus a wide distribution of diseases among domesticated 
animals due to a group of bacteria closely resembling and probably 
identical with swine-plague bacteria. Some diseases attack several 
species at the same time ; others are, so far as we know, restricted to one 
species. We have also seen that there is a wide distribution of attenu- 
ated varieties among the same domesticated animals in the healthy 
state, inhabiting, so far as our investigations have gone, the upper air 
passages. Some observers are inclined to regard these different bac- 
teria as practically the same. Hiippe has proposed the name scpticfcmia 
hccmorrhagica for all the forms of disease caused by them. Other ob- 
servers hesitate to accept at present this unifying explanation. For 
practical purposes the following explanation, based on quite extended 
study of this group of bacteria, may serve as a provisional guide in the 
prevention of disease. 

The real test of the power of any bacteria to produce disease is viru- 
lence. The greater the virulence the more liable will be the disease to 
spread from one species to another. This is strikingly illustrated by 
the Wildseuche of Bollinger. The relative virulence can be accuratel^^ 
determined only by careful series of inoculations upon small and large 
experimental animals, performed in precisely the same way hi each case 
with pure cultures of the bacteria. Again, the power of a given disease 
to i>ass from one species to another frequently remains unnoticed, partly 
because the opportunity for such transmission is rarely given. Animals 
of different species, such as swine, cattle, and sheep, are rarely raised 
and kept in the same inclosures, because the nature of food required 
for each, and other conditions lead to specialization in stock-raising 
and tend to restrict each species to its own pasture ground. 

It is not unreasonable to suppose that bacteria living in the air pas- 
sages of one species, and harmless to it to a certain degree, may prove to 
be disease germs with reference to another species. Thus the attenu- 
ated bacteria living in the air passages of healthy cats, dogs, pigs, and 
cattle, are all fatal to rabbits. In general, the larger and more powerful 
the animals the less effect disease gertns have upon them. It is there- 
fore probable that some of the outbreaks of swine disease in the West- 
ern States may be due to the cattle with which the swine are herded 
for feeding purposes. The bacteria in cattle, harmless to them, or per- 



145 

haps causing only mild disease and rarely observed, may prove the start- 
iiij;- point of disease tor swine. 

Wliih^ we have no [)()sitive demonstration of these statements, it is 
desirable that those engaged in stoclc-raising should have their att«Mi- 
tion called to the possibilities embodied therein. 

5. ON MEASURES TO 15E TAKEN IN THE PREVENTION OK SWINE PEACaiE. 

In regard to the general measures to be taken and the rules to be 
observed in the prevention of hog cholera and swine {)lague, we refer 
the reader to the report of the Secretary of Agriculture for L88.S, page 
15G, or the report of the Bureau of Animal Industry for 1887-88, page 
148, or the Special lieport on Hog Cholera, 1889, page 123. The rules 
and directions there formulated are adapted as well to swine i)lague, for 
the bacteria of the latter disease are even more easily destroyed by vari- 
ous agencies than are hog-cholera bacilli. In the following pages only 
the most important i)oints are touched upon. 

Tiie things with which healthy swiue should not come in contact are, 
in the order of their importance, first of all, diseased herds and ani- 
mals, strange swine the history of which is not known, offal from estab- 
lishments using carcasses of swiue, recently infected ground, railroads 
carrying swine, and polluted streams. Soil and water nuiy be infected 
by living and dead swine or any olTal from them. 

When the disease has actually appeared in a herd the question gen- 
erally arises whether it is worth while to make any attempts to save a 
l)ortion of the herd or to leave them to their fate. As a rule it may be 
stated that it is best to slaughter both healthy and diseased at once and 
give the surroundings sufficient time to rid themselves of the infection 
before fresh animals are brought into them. If this be not desirable we 
should recommend the following measures to be rigorously carried out: 

{(() Itemoval of still healthy animals to uninfected grounds or pens 
as (piickly as possible. 

(h) Destruction of all diseased animals. 

(c) Careful burial or burning of carcasses. 

{d) Repeated thorough disinfection of the infected premises. 

{e) Great cleanliness both as to surroundings and as regards the 
food. 

If the animals have been removed to uninfected grounds, careful 
watching is necessary to remove therefrom at once all swiue which 
show signs of disease. 

Among the various disinfectants which can be recommended are the 
following: 

1. Slaked lime, in the proportion of about 5 per cent (one-half pound 
of lime to a gallon of water). 

2. Equal volumes of crude carbolic acid and ordinary sul])huric acid 
mixed together and added to water in the proportion of 2 ounces to a, 
gallon of water (1^ volume per cent). 

1G14— .— "10 



146 

3. Siilpliuric acid added to water iu the proportion of 1 ounce to a 
gallon. 

4. Boiling water. 

5. Corrosive sublimate (mercuric chloride) in the i^roportion of 1 
drachm to a gallon of water (1 to 1,UU0). 

Solution No. 2 is said to be more active if, while the sulphuric acid is 
beiug added to the crude carbolic acid, the vessel containing the latter 
is i)laced in cold water to prevent undue heating of the liquid. 

It should be borne in mind that sulphuric acid and corrosive subli- 
mate attack metals, and that the solutions are best made in wooden 
pails, etc. Corrosiv^e sublimate is also highly poisonous, and the solu- 
tion should not be made stronger than indicated. The lime is, on the 
whole, the best and chea])est, but it may not be desirable to ijse it every- 
Avhere; hence, one of the others may be substituted. Each of the sohi- 
tions recommended is more than strong enough to kill both hog-cholera 
and swine-plague bacteria and they need not be increased in strength. 

When swine have become infected while ruuningover tracts of ground, 
disinfection of such tracts may be regarded as practically inipossible. 
If, however, they have been brought up in pens or in small inclosures, 
disinfection should be thoroughly carried out. The woodwork of pens 
may be disinfected by exposing all portions, cracks and corners, to the 
action of any of the solutions mentioned. These may be applied with 
a broom or any other household article which insures uniform wetting. 
Whitewash is useful for woodwork of fences, etc., when there is no ob- 
jection to its appearance. Its action is only exerted at the time of 
application and after it has dried it will not destroy bacteria subse- 
quently adhering to it. It must, therefore, be applied fresh every time 
disinfection is needed. For large farms some kind of spraying appa- 
ratus would be of great service in insuring uniform distribution of the 
disinfectant. In the selection care must be exercised, however, owing to 
the corrosive action of some of the solutions. The disinfection of the 
surface of the soil over small areas is perhaps best accomplished by the 
slaked lime or the crude carbolic-acid solution. It should bo remem- 
bered that both preparations may be irritating to the feet of animals 
immediately after they have been applied. The feeding troughs should 
receive special attention, and after the application of the disinfectant 
this should be washed away with water, j)referably hot or boiling. 

The directions thus far given apply mainly to the prevention of dis- 
ease. When animals have been actually attacked, can anything be 
done for them ? It has already been stated that treatment of commu- 
nicable diseases is not a desirable thing, but even if it were the deaths 
follow each other so rapidly in many outbreaks that there is no time 
for the application of remedies. If, however, an effort to treat them is 
to be made, it is desirable to avoid the various specifics and remedies 
of unknown composition, some of which, thoroughly tested at the Bureau 
Station by Dr. F. L. Kilborne, were of no avail in checking the disease. 



147 

Tlie sick anin-als should be isolated one from another, as far as possi- 
ble confined in small inclosures, kept (piiet, and fed with moderate 
quantities of food, preferably with millc, if this is to be obtained. If 
the swine are bein*? fattened when the disease appears, this process 
should be stopped at once and a light diet substituted. Tiie tendency 
towards the localization of disease in the large intestine, in both swine 
l)lague and hog cholera, seems to be due, at least in part, to the con- 
stipated habits of the pig, which permit the pathogenic bacteria to re- 
main long enough in the intestine to act injuriously upon the mucous 
membrane. Constipation is not easily overcome, as the trials with vari- 
ous cathartics* have demonstrated, and it is highly important when 
the disease has appeared to feed a greater variety in small quantity or 
to follow the recomiriendatiou of giving the digestive organs a complete 
rest by feeding milk. The boiling of food may be desirable, inasmuch 
as it destroys any disease-producing bacteria which may be present, 
and makes digestion easier. An experiment carried out at the Bureau 
Station with boiled food did not show any more favorable results, how- 
ever, than with unboiled food ordinarily given, so that we can simply 
suggest it for further trial. 

Even if treatment should succeed after much trouble ami expense to 
save some few swine, it may not be profitable, owing to the injury in- 
flicted on the various organs during the disease. The lungs are, as a 
rule, seriously affected. They may become adherent to the walls of the 
thorax, and the pericardium may become firmly attached to the heart 
and impede its action. These permanent injuries, which no kind of 
treatment yet suggested can avoid, exercise an injurious influence on 
the proper development of the animal affected and make its raising of 
questionable advantage. It has already' been stated that such recov- 
ered animals may for a time at least be dangerous as carriers of the dis- 
ease germs to other swine. 

The only encouraging line of action, therefore, lies in the prevention 
of disease by the observance of suitable precautionary measures and 
in that general practice of hygienic laws which thus far has been the 
only means of checking the rapid spread of epidemics in the human 
family. The method first suggested by Pasteur of inoculating animals 
with attenuated cultures, to make them resist any and every attack of 
a given infectious disease, is, theoretically considered, the simplest 
means of prevention. Practically, however, there are two objections 
wliich are growing in importance year by year, as our knowledge of 
infectious diseases is becoming broader and deeper. The method of 
Pasteur may distribute the specific bacteria far and wide and become 
a source of future evil, since we do not know but that the attenuated 
bacteria may in some way regain their former virulence. The other 
objection rests on the fact that diseases differ so much one from the 
other that the method seems to insure success in only a few diseases. 

* Special Report on Hog Cholera, 1889, p. 135. 



148 

As regards swine plague, the experiments which have thus far 
been carried out indicate that this disease may prove amenable to pre- 
ventive inoculation. We have been able, by the injection of both living 
cultures and those sterilized at a low temperature (580 (i.)^ to make 
the most susceptible animals, rabbits, insusceptible to the most virulent 
swine-plague bacteria. By two subcutaneous injections of cultures of 
swine-plague bacteria swine have been made insusceptible to doses in- 
jected into the circulation, which proved fatal to "control" pigs within 
24 hours. In the preliminary experiments upon rabbits, designed to 
produce immunity, several methods were employed.* 

1. Minute but gradually increasing quantities of culture liquid of very 
attenuated swine-plague bacteria were injected at different intervals 
into the ear vein of rabbits. Only a very small proportion of these sur- 
vived the test inoculation with very virulent swine-plague bacteria. 

2. Sterilized bouillon cultures were injected into the abdomen and 
into the circulation of rabbits. This method also produced immunity 
and partial resistance, but iu only a comparatively few animals. 

3. The preceding method was modified in the following manner : 
Swine-plague bacteria from outbreak IX were allowed to produce for 
2 days a rich growth upon agar. This growth was scraped off and a 
very turbid suspension in bouillon prepared and sterilized at 58° 0. 
With this sterilized suspension injections were made into the abdomen 
of rabbits as follows: 



Eabbit No. 


May 4. 


May 8. 


May 14. 


May 22. 


Total. 


Keiuavks. 


35 


cc. 
1.5 
1 
.5 


cc. 

1 
. 5 
1.5 

2 


cc. 

2 
2 
2 

2 


cc. 
3 
3 


cc. 

,.5( 
7.5^ 
7.5 

4.5 


Kos. 35, 36, and 37 inoculateil with 
viriileut swine plasue May 2fi. 
Check dies over nijrht. All three 


36 

37 


38 


action, 
liiooulated with virulentswine plague 






May 19, die.s iu 6 day.s with severe 
local reaction, iilenritis, and peri- 
carditis. The check dies iu 16 to 20 
hours. 



These results show very decisively the protective effect of the steril- 
ized growth of swine-plague bacteria. Additional experiments have 
not yet been made. 

In conjunction with Dr. Kilborue, the protective effect of swine-plague 
cultures was tested upon swine in the following experiment : Seven pigs 
belonging to the same lot and about 4 months old were chosen, three 
of which were set aside as " control" animals or checks. The remain- 
ing four received February 28, 1891, a subcutaneous injection of cubic 
centimetres of peptone-bouillon culture of virulent swine-plague bac- 
teria (outbreak IX), one-half into each thigh. As a result one died.t 
The remaining three were reinoculated in the same way March 14, 

* These oxperinieuts wore carried out in coujuiiction ^vitl^ Dr. V. A. Moore. 
t See p. 74 for autopsy notes. 



149 

receivin;^- on this date 10 cuhic centimetres of enlture liquid. April 3, 
these, to^etlier with the three control animals or cheeks, received the 
linal test inoculation; 2 cubic centimetres of peplone-bouilhni culture of 
the same bacteria were injected into a vein of the leg of each animal. 
Two of the control animals died within 24 hours, the third in 30 hours. 
None of the three vaccinated animals became ill. No symptoms of dis- 
ease or lesions appeared subse(|uently. 

These experiments simply demonstrate the fact that swine may be 
protected from fatal doses by subcutaneous injection. Whether this 
process would be successful in natural outbreaks can not be inieired 
■from this test. The method is oi)en to the objec^tion above mentioned, 
i. ('., it is liable to distribute the specific bacteria wherever vaccination 
is practiced. Since the more desirable oiu^. of inje(;ting the products of 
bacterial growth is now being tested there is no need of any further 
discussion of this subject at the present time. 

CONCLUSIONS. 

1. There are two independent infectious diseases of swine — swine 
])lague and hog cholera — each caused by an easily recognizable, specific 
disease germ. 

2. Swine plague (in those outbreaks which have come to our notice) 
is limited chiefly to the lungs in its destructive effect. The intestines 
maybe and frequently are involved in the disease ])ro(;ess. Hence it is 
an infectious pneumo-enteritis rather than an infectious pneumonia. 

3. There is considerable variation in the virulence or disease-produc- 
ing i)Ower of swine-plague bacteria from different outbreaks. The 
^greater the virulence, other things being equal, the severer ami more 
extensive the epizootic. 

4. The bacteria of ^chiceineseuche {GGrman disease of swine) are iden- 
tical with those of swine plague. 

5. In the upper air passages of a certain percentage of health}' swine, 
cattle, dogs, and cats, bacteria exist which belong to the species of 
swine plague bacteria, and which as a rule possess a relatively feeble 
virulence. While it is probable that such bacteria may produce disease 
it may be regarded as pretty certain that it is largely aided by second- 
ary causes producing unthriftiness, and is merely sporadic and not 
communicable. 

6. In many epizootics of swine disease both hog-cholera and swine- 
plague bacteria as well as the respective lesions of these bacteria co- 
exist. Such mixed diseases are due to the frequent presence of both 
bacteria in the surroundings of swine, probably a result of frequent in- 
troduction. Either disease may be primary according to its relative 
virulence. 

7. It is highly probable that the many attenuated varieties of either 
disease germ can i^roduce disease only when assisted by the other germ 



150 

or by the iiTisanitary, nnphysiological methods of rearing swine by which 
the latter are reduced in vitality and uiade more susceptible. 

8. It is pretty well established that there are a number of infectious 
diseases aftectiug cattle, bufl'aloes, deer, fowls, and smaller animals, 
the bacteria of which are closely related, if not identical with, those of 
swine plague. These plagues appear in various parts of the globe spo- 
radically. ( Wild- und Kinderseuche, harbone hnfaJino, fowl cholera, rab- 
bit septicaemia.) Their tendency to spread from one species to another, 
from cattle to swine, for instance, probably depends both on the degree 
of virulence of the bacteria as well as the opportunities afforded for 
such transmission. 

9. Swine-plague bacteria are verj^ probably introduced into a herd 
only in the bodies of animals, since they are speedily destroyed in soil 
and water by natural agencies. Viruleni; varieties are perhaps always 
derived from preexisting disease. Attenuated varieties may be intro- 
duced by healthy animals. Since these may under special conditions 
give rise to disease, efforts to prevent and suppress infection must take 
into account the physical condition of the exposed animals. 



APPENDIX. 



PRESENCE OF SEPTIC BACTERIA, PROBABLY IDENTICAL WITH THOSE OF SWINE 
PLAGUE, IN THE UPPER AIR PASSAGES OF DOMESTICATED ANIMALS 
OTHER THAN SWINE. 



By Veranus a. Moore, B. S., M. D., Assintant. 



The examination of the secretions of the mucous membrane of the 
upper air passages in domesticated animals otlier than swine was be- 
gun under the direction of Dr. Theobald Smith for the purpose of deter- 
miuing whether or not the swine-plague germ, or a genu closely related 
to it, is normally present in these animals. The results obtained from 
the limited number of examinations that have been uiade from the 
various aniuials are of so much value in throwing light upon the natural 
habitat of this grouj) of micror»rganisms that a preliminary report of 
these experiments seemed desirable at this time. 

The methods that have been employed in these investigations are the 
same as those used by Dr. Smith iu the examination of mucus from 
the respiratory tract of healthy pigs, and which are described on p. 
110 of this report. The inoculations of rabbits with the mucus from 
the various animals were made in part conjointly with Dr. F. L. Kil- 
borne, in part by him alone, and in a few cases I alone am responsible 
for these operations. 

1. Tnoculations from cattle. — Rabbits have been inoculated with the 
mucus taken from the larynxoramygdaloid cavities of seven healthy cat- 
tle. Four of these were steers, two of which were Western animals that 
had been shijiped to Washington for beef. The four steers were killed 
in a slaughter-house near the Experiment Station by cutting the blood 
vessels in the neck. Care was taken to keep the mouth free from blood. 
The other three were heifers that were killed for various purposes iu a 
similar manner at the Experiment Station. In each case the mucus was 
collected immediately after the death of the animal and inoculated sub- 
cutaneously into rabbits. 

The rabbits that were inoculated with the mucus from the four steers 
and one of the heifers died iu from 3 to days. The lesions found in 
these rabbits were similar to those produced by the attenuated swine- 

If)! 



152 

plague germ. The local infiltration contained several forms of bacteria. 
In tlie ])eritoneal exudate and in the spleen and liver bacteria were 
found that resembled the swine-plague germ both in stained cover-glass 
I)reparations from the tissues and in cultures. 

The rabbits inoculated from the two remaining animals showed no 
signs of disease. 

The pathogenic effect of the bacteria obtained from the first two cat- 
tle was determined by inoculating rabbits with pure cultures. The 
subcutaneous iuTection produced extensive purulent iufiltration at the 
l)oint of inoculation and exudative peritonitis, destroying the rabbit in 
G days. An intravenous inoculation of the same quantity of a similar 
culture from the second case proved fatal in 24 hours. The blood, liver, 
and spleen contained innumerable bacteria which could not be distin- 
guished from the swine-plague germ. No inoculations were made with 
pure cultures from the remaining three animals. It is sufficient to say 
that the lesions produced in all of the rabbits inoculated from the five 
cases were the same. The following tables will explain the results of 
these inoculations : 

Inoculation of nibhits with mucus from the upper air passages of cattle. 



Ani- 
mal 
No. 


Mucus 
Iroia— 


Rabbit 
inocu- 
lated, 
No. 


Date of 
inocula- 
tion. 


Rabbit 
died 
in— 


Remarks. 


1 

2 

3 

4 
5 

C 

7 


A myg d a- 
loid cav- 
ities. 

Larynx ... 

Amygda- 
loid cav- 
ities. 

... do 

... do 

Larynx . . . 

Amygda- 
loid cav- 
ities. 


I 2 

\ ' 

5 
6 

I I 

C 10 
( 11 


1890. 
Feb. 27 

Fob. 27 
Feb. 27 
Feb. 2T 

Mar, 13 

Apr. 1 
Mar. 20 
Oct. 2 
Oct. 2 

1891. 
Jan. 5 

Jan. 5 


Days. 
3 

4 
4 

4 

3 

4 

'""4 
C 


Local reaction; peritonitis. 

Do. 
Local reaction; peritonitis; pleuritis. 
Local reaction ; peritonitis ; pleuritis and pericar- 
ditis. 
Local reaction ; peritonitis. 

Local reaction; peritonitis; beginning pleuritis. 
Rabbit remained well. 
Local reaction ; peritonitis. 
Do. 

Rabbit remained well. 

Do. 



Inoculntions with pure cultures obtained from above rabbits. 



Culture 

from 

rabbit 

No. 


Method of inoculation and date. 


Rabbit 
died 
in- 


Remarks. 


1 
3 


March 4, 1890, one-eighth cubic centimetre bouillon* culture 

subcutaneously. 
March 4, 1890, one-eighth cubic centimetre bouillon culture 

into ear vein. 


Day*. 
6 

1 


Local reaction ; 

peritonitis. 
Septiciomia. 



' All the bouillon used in these investigations contained one-fourth per cent, of peptone. 



2. Inoculations from cats. — Babbits were inoculated with the secre- 
tions of the mucous membrane of trachea, larynx, or pharynx of seveu 



153 



hcaltliy cats. The cats were raised in and about Wasliinj?ton, but not, 
on the p].\[)eriment Station. J'hey were killed eitlier by a shot tiironj;li 
tlie heai't or with chh)roibnn, and the nuieus was removed with every 
precaution immediately after death. 

The rabbits that were inocnhited from cat No. G remaitu^d well. All 
of the others died. The residt of these inoculations is of i)articular in- 
terest, as the rabbits died in from 1 to 7 days, and presented hisions sim- 
ilar to those produced by the swine-plague germ in its most virulent as 
well as its attenuated forms. From tlie various organs of all the rab- 
bits bacteria were fouiul which could not be distinguished from each 
other or from the swine-plague germ. 

The virulence of pure cultures obtained from the rabbits inoculated 
trom cats 1, 2, and 3 was tested by both intravenous ami sul)cutaneous 
inoculations on fresh rabbits. These proved fatal in from IS to 4.8 
hours. The blood and other organs contained innumerable bacteria. 
The cultural characters of these germs will be mentioned in another 
l)lace. The accom[)anying tables give a summary of these inoculations: 

Jiiocidation of rabhitu with mucua from lite upper air passage>i of cats. 



Oat 
No. 


How killed. 


Mucus 
from— 


Rabbit 
inocula- 
ted, No. 


Date of 
inocula- 
tion. 


Rabbit 
died in— 


Remarks. 


1 

2 

3 
4 
5 

6 

7 


Shot througb 
bcait. 

. . do 


[Larynx .. 
do ... 


C 12 
i 13 

( 14 

i \^ 

1« 

17 

18 

< 19 
) 20 
( 21 
i 22 


1890. 
Apr. 22 
Apr. 22 

Apr. 22 
Apr. 22 
Juno 11 
June 11 
Dec. 2G 

1891. 
Jan. 6 
Jan. C 
Jan. 2t 
Jan. 24 


Days. 
13 

7 

2 
3 
1 
1 
li 


Local reaction; peritoniti.s 

Local reaction ; peritonitis, pleuri- 

tis, pericardilis. 
Local reaction ; peritonitis. 

Do. 
Septicemia. 

Do. 
Slight local reaction, licKinnin;; per- 
itonitis. 

Rabbit remained well. 

Do. 
Local reaction; beginning plouritis. 
Local reaction ; pleurilis. 


...do 

do 


Pharynx. 
do 


...do 

Chloroformed 
do 


Larynx . . 

Trachea . 
do 


3 
5 







Inoculations with pure cultures obtained from above rahbits. 



Culture 
from rab- 
bit No. 


Method of inoculation and date. 


(Rabbit 
died in— 


Remarks. 


14 
15 
16 


A nr.20, 1890, one-eighth cubic centimetre bouil- 
lon culture into ear vein. 

May 2, 13J0, loop agar culture subcutaneously 
in ear. 

May 10,1890,oneeighth cubic centimetre bouil- 
lon culture into ear vein. 

May 10, 1890, one-eighth cubic centimetre bonil- 

lon culture subcutaneously. 
... do 


Hours. 
20 

60 

18 

36 

18 


Septicajraia. 

Beginning peritonitis. 

Septicaimia. 

Slight local reaction ; sep- 

ticaMuia. 
Septicemia. 





3. Inoculations from dogs. — Rabbits were inoculated with the mucus 
taken from the larynx or u[)i)er pharynx of six healthy dogs. These 
were also procured in Washington City and its suburbs. They were 
killed by a shot through the heart. The mucus was removed imme- 
diately after death and at once inoculated. 



154 

The rabbits inoculated from dogs ^os. 2 and 3 died in about 36 hours 
Innumerable bacteria were found in the various organs that coukl not 
be distinguished from those obtained from cattle and cats or from the 
swine-phigue germ. The rabbits inoculated from the other four dogs re- 
mained well. Both subcutaneous and intravenous inoculations of fresh 
rabbits with cultures of these bacteria proved that they were as viru- 
lent as those from several of the cats. The results of these inoculations 
are summarized in the appended tables: 

Inoculation of rabbits ivith mucus from the upper air passages of dogs. 



Dog 
No. 



Mucus 
from — 



Rabbit 
inocula- 
ted, No. 



Larynx . . 

Pharynx. 
Larynx . . 
..-.do.... 

..do.... 

..do.... 



Date of Kabbit 
inocula- died 
tion. 



1890. 
Apr, 25 
Apr. 25 
Apr. 28 
May 9 
May 26 
May 31 



29 Dec. 6 



Mours. 



Kemarks. 



Rabbit remained well. 

Do. 
Local reaction, beginning pleuritis. 
Local reaction, penloiiitis. 
Rabbit remained well. 

Do. 

Do. 



Inoculations tvitJi pure cultures obtained from above rabb 



its. 



Culture 
from 

rabbi t 
No.— 



Method of inoculation and date. 



May 2,1800, loop agar culture subcntaneouslv in 

ear. •' 

May 20, 1890, one-eighth cubic centimetre bouillon 

culture into ear vein. 
May 20, 1890 one-eighth cubic centimetre bouillon 

culture subcutaneously. 



Rabbit 
died 



Hours. 
22 



Remarks. 



Sepdcremia. 
Do. 
Do. 



4. Inoculations from other atiimals. ^Bahhits have been inoculated 
with the mucus taken from the larynx or trachea of one sheep, one 
horse, two old fowls, and one rabbit. One of the two rabbits inocu- 
ated from the sheep developed a large abscess near the point of inocu- 
lation. It was chloroformed after about one month. There were no 
other lesions. The other rabbits remained well. The inoculations from 
a single animal are, of course, insufficient to give any general informa- 
tion respecting the species. The aunexed table gives all the informa- 
tion necessary with reference to these inoculations. 

Inoculations u'ith mu(ms. 



Animal. 



How killed. 



Mucus 
from — 



Sheep 1 .. . 

Horse 1... 

Fowl 1.... 
Fowl 2.... 

Rabbit 1.. 



Cutting jugulars. 
Shot 

Neck broken 

do 



Larynx . . 

--.do .... 

Trachea . 
...do .... 



Chloroformed do 



Rabbit Date of 
inocula- inocula- 
ted, No. tion. 



Remarks. 



1890. 
Apr. 
Apr. 
Apr. 
Juno 
June 
June 

1891. 
Apr. 



Local abscess; chloroformed 
Rabbit remained well. 

Do. 

Do. 

Do. 

Do. 

Do. 



155 

It will be seen from the experimeuts given that a jjerm which is not 
distinguishable from the swine-plague germ was found in the mucus 
from the u[)i>er air i)assages of 71 per cent, of the cattle, 85 per 
cent, of the cats, and 33 per cent of the dogs from which inocula- 
tions were made. When the rabbit lived for more than 24 hours 
after its inoculation there was a purulent infiltration of the skin and 
subcutis at the point of inoculation. The infiltration extended over an 
area varying in size in proportion to the length of time which the animal 
lived. In some cases it covered the entire ventral aspect of the body. 
Occasionally there was in addition a sanguinolent effusion which ex- 
tended beyond the limits of the infiltration. The local reaction was 
undoubtedly increased by the presence of other bacteria that were in- 
troduced with the mucus. The internal lesions were characterized by 
an inflammatory condition produced by the localization of the germs 
on some one or more of the serous membranes, notably the peritoneum, 
when the rabbit did not die from a rapidly fatal septic;emia. 

It is interesting to note that the inoculations made from cattle proved 
fatal in from 3 to G days, and that the resulting lesions in every instance 
were characteristic of attenuated swine plague. In the rabbit that 
lived G days there was severe peritonitis, while in three that lived only 
4 daj's there were both peritonitis and pleuritis and in one case i)eri- 
carditis. The rabbit which lived G days after inoculation with a pure 
culture exhibited in addition to the local reaction only peritonitis. 

In the inoculations from cats we find a much wider range in the char- 
acter of the lesions produced. The rabbits inoculated from cats Nos. 3 
and 4 were victims of a rapidly fatal septicu'inia, the swine-plague bac- 
teria being distributed in enormous numbers throughout the blood and 
internal organs. The rabbit inoculated from cat No. 5 lived about 12 
hours longer and exhibited beginning peritonitis. The localization of 
these germs on the peritoneum is further illustrated in rabbits Nos. 12, 
14, and 15. These animals lived 2 and 3 days and died with exudativ^e 
peritonitis. In the exudate there were innumerable bacteria, but com- 
l)aratively few were found in the blood. In rabbit 13 we have a marked 
example of the distribution of these germs over the entire serous sur- 
faces of the trunk. Both rabbits from cat No. 7 are interesting, as the 
lesions were confined to the pleura. In these cases the pleuritic exu- 
date contained innumerable swine-plague bacteria while the blood con- 
tained only a few. This emphasizes the fact that in cases of well- 
marked localization there are comparatively few germs in the general 
(;irculation at the time of death. 

The rabbits that were inoculated from dogs Nos. 2 and 3 lived the 
same length of time as the rabbit inoculated from cat No. 5. It is in- 
teresting to note that the rabbit inoculated from No. 2 exhibited pleu- 
ritis and the one from dog No. 3 peritonitis. Here again we have a 
marked illustration of the variable localization of this group of micro- 
organisms when their virulence is not sufficient to destroy the rabbit 



156 

in fi-om 18 to 24 hours. The tendency to localization is well shown in 
the following suni.nary of the lesions found in the nineteen rabbits that 
Have succumbed to the inoculations from the different auimals: 

Sum7)\jary. 



Lesions. 



Local reaction, pin-itonitis 

Local reactioi), iileuritis "' 

Local reaction, peritonilis, aiiil pfe'iiriVis 

S°Tic-B^mf ''*"' 1"^^'^'^**""^'^' Pl'iiiiitis, and pericarditis' 



No. of 
rabbits. 



Per cent. 



52. G 
15.7 
10. 5 
10.5 
10.5 



,, T^^e Inoculations with pure cultures of the bacteria obtained from 
the different rabbits, although few iu number, are important, as they 
verify the results obtained from the original inoculations. The sub- 
cntaueous inoculation with one-eighth cubic centimeter of a bouillon 
culture of the germ from cattle resulted in extensive local reaction 
and peritonitis. The inoculation of a rabbit subcutaneously in the 
ear with a loop of an agar culture from cat No. 1 is also interesting 
as It not only lived nearly as long as the original rabbit, but devel- 
oped peritonitis. The rabbit inoculated subcutaneously with a culture 
from cat No. 2 is the only rabbit in these experiments that lived over 
24 hours without exhibiting some point of localization of the germs on 
the serous membranes. 

The difference in the virulence of the germs obtained from cattle, cats 
and dogs, and the consequent variations in the character of the lesions 
produced in rabbits, are paralleled in similar inoculations from pigs and 
with cultures of the swine-plague bacteria obtained from sporadic cases 
and the different outbreaks of that disease, I have, therefore, not 
found in the inoculations of rabbits any pathogenic property possessed 
by any of the septic germs discovered in the upper air passages of 
he^iUhy animals that will differentiate them from the swine-plague bac- 

Gultural characters.-From the blood or spleen of each rabbit cultures 
were made on agar or in bouillon. From these, subcultures were made 
in the various culture media employed in differentiating bacteria for 
the purpose of determining, if possible, any cultural differences that 
might exist between them, or between them and the swine-plague bac- 
teria. As these cultures were obtained at different times and the media 
used prepared on different dates the occasional slight variations in the 
character of the growth that were observed between the different bac- 
teria could not be considered as constant differences, as it was found 
that these bacteria, like those of swine plague, do vary slightly in cul- 
ture media. In view of this fact two series of comparative cultures 
have been made on the different media, each medium being prepared 
trom the same material and at the same time. 
The comparative cultures were made (1) from cultures of bacteria ob- 



157 

tallied from a liealtliy pig, cat, and dog; (2) from cultures of attenuated 
and of viruleut swine-pla<;ue bacteria, and (3) from cultures of .swiue 
l)lague bacteria found in a <;uiiiea -pig that died of si)oiadic pneumonia. 
Unfortunately the germs from the upper air passages of cattle had 
perished at the time the comparative cultures were made. 

(a) Xiitrieitt agar. — The growths of tbo Various bacteria upon tbis sii1)stratuiii were 
uot distinguisbable ouo from the otber. 

(b) Alkaline peptonized houiUon. — Tbo growth in the bouillon cultures uiado from 
the blood or spleen of a few of the rabbits consisted of small, grayish Hakes. These 
were at first held in suspension in the liquid, but soon settled, leaving the supernatant 
culture fluid perfectly clear. This character was uot constaut, as the clumps of 
growth gave way to a uniform cloudiness of the culture liquid after a short scries of 
subcultures. The bouillon cultures from all of the other rabbits wei"e uniformly 
clouded. 

In the first series two of the germs grew in clumps. The others imparted a uniform 
cloudiness to the lic^uid. After 7 days standing the growth had settled in the bottom 
of the tube iu the two cultures thatcontained clumps. In the others a thin, grayish, 
somewhat viscid band composed of bacteria was formed on the sides of the tube at 
the surface of the liquid. The latter was faintly clouded. The growth of the viru- 
lent swine-plague germ seemed less vigorous than that of the others. In about '.i 
weeks there was a considerable quantity of a grayish, viscid sediment iu the bottom of 
the tubes which upon agitation was forced up, ajjpearing as a somewhat twisted, tena- 
cious cone with its apex at the surface of the liquid. 

In the second series the growth in all of the cultures imparted a uniform cloudiness 
to the liquid. In 48 hours the virulent swine-plague culture was nearly cleared. In 
7 days the cultures of the bacteria from the healthy pig and cat aud from the guinca- 
])ig's lung were clear. The cultures of the attenuated swine-plague germ and the 
germ from the healthy dog remained clouded. In every case the grayish band formed 
DM the sides of the tube at the surface of the liquid as in four of the cultures in the 
first series. The sediment in the bottom of the tubes was small in quantity and fria- 
ble. The reaction of all of the cultures was decidedly acid after "24 hours ; less 
strongly so after 4 weeks. The difference in the character of the sediment in the two 
series of cultures was very marked. This same variation has been observed in other 
bouillon cultures of the same bacteria. It is important to add that the variation in 
the character of the growth iu bouillon cultures of any one of these germs has been 
found to be as great as that between cultures of the bacteria from different sources. 

Although these bacteria change the reaction of an alkaline bouillon to an acid 
one during their multiplication, they will not grow when inoculated into peptonized 
beef-broth that has not been neutralized. 

(c) Peptonized houillon containing 2 per cent, glucose. — The growth of the various 
bacteria iu fermentation tubes containing this li(|uid does not vary in the cultures * 
examined. 

(ri) Gelatine. — The growth in this medium is uncertain. The germ from cat No. 2 
developed minute grayish colonies in roll cultures. They were, however, too small 
for diagnostic purposes. One of the swine-plague germs occasionally developed mi- 
nute colonies. The other bacteria did not grow, although a large number of cultures 
were made from each. 

(e) Potatoes. — No growth. 

(/) Milk. — No appreciable change iu the appearance of the milk was produced. 
Slightly acid in reaction. Cover-glass preparations showed a vigorous multiplication 
of the bacteria iu every culture. In this medium the bacteria appeared as rods 
longer than under other conditions under which they have been <!xauiiue(l. 

From both the comparative cultures and the large number of cul- 
tures that have beeu made at other times, I have thus far been unable 



158 

to detect any cultural character that is sufficiently constant to differ- 
entiate the bacteria in question, the one from the other. 

PNEUMONIA AND PLEUBITIS IN A GUINEA-PIG CAUSED BY BACTERIA 
CLOSELY RESEMBLING THOSE OF SWINE PLAGUE. 

On December 24, 1890, a large adult female guinea-pig was found 
dead in a pen where several of the supply animals were kept. A care- 
ful examination of this animal revealed the following conditions : 

Beneath the skin near the left mamma a closed absceos. Swelling and ulceration of 
the left fore foot. Spleen normal. Liver fatty. No intestinal lesions. In the plenral 
cavity a considerable qiiantity of a grayish, viscid exudate lining the costal and 
pulmonary pleura. The anterior half of both lungs hepatizod. Suppurative peri- 
carditis. Cover-glass preparations from the pleural exudate contained a very large 
number of bacteria not distiuguishal)le from swine-plague bacteria. In an agar tube 
inoculated with the exudate a pure culture of these bacteria developed. 

A rabbit inoculated subcutaneously with a very small ({uautity of the pleural exu- 
date died in less than 20 hours. Innumerable swine-plague bacteria were found 
in the liver, blood, and spleen. The polar slain so characteristic of the swinc-plague 
germ was well marked in the cover-glass preparations from all of the tissues. A pure 
culture of this germ was obtained from the blood. 

In order to test still further the virulence of this germ, a second rabbit was inocu- 
lated subcutaneously with an equivalent of one-five hundredth cubic centimetre of a 
bouillon culture made from the blood of the first rabbit. This inoculation proved 
fatal in about 24 hours. Innumerable swine-plague bacteria were found in the 
various organs. 

The cultures of this germ on the various media could not be distin- 
guished from those of the virulent swine-plague germ. 

Dr. Kilborne informs us that prior to the death of this guinea-pig, of 
which a bacteriological examination was made, others had been found 
dead from time to time at the Experiment Station without exposure to 
any disease. A cursory examination had shown that a considerable 
number of these had died from exudative pleuritis with or without 
pneumonia. 

DISEASE IN A FOWL ASSOCIATED WITH BACTERIA CLOSELY RESEM- 
BLING THE FOREGOING. 

On April 31, 1891, two large, well-nourished hens were found dead in 
a flock of fowls that are kept on the Experiment Station. A few days 
prior to this a fowl had died, but it was not examined. There had 
been no evidence of a contagious disease in the flock up to this date, 
and no deaths occurred subsequent to the ones reported here. A careful 
examination of these fowls showed that one contained bacteria closely 
resembling swine plague, and that in the other there was an extensive 
croupous exudate throughout the larynx and trachea, the specific cause 
of which was not determined. 

Fowl I. This fowl was sick 2 days before its death. Heart muscle pale ; in right 
ventricle a mixture of a pale and dark gelatinous clot. Liver sprinkled with a few 



159 

grayish spotK, apparently necrosed tissue. Spleen normal. Kidneys iujeeted with 
urates and enhir^ed. Trachea and <esoplia,>ins normal. On cover-glass jireparations 
from the liver are minute bodies which appeared to be bacteria. Tul)es of agar 
inoculated with a bit of the blood and liver developed a rich grayish growth not 
distinguishable from an agar culture of swine-plague bacteria. 

April '^4 a rabbit was inoculated subcutaueously with a very small ([uantity of the 
growth from the blood culture. The rabbit died in 20 hours. Innumerable swino- 
plague bacteiia in the various organs. The polar stain was very marked in stained 
cover-glass preparations. Pure cultures of the same bacteria were obtained from the 
blood. 

April 28 two fowls were inoculated with an agar cultuiv; from the blood of fowl 
No. 1. The surface growth of the agar culture was diluted with about 1 cubic cen- 
timetre of sterilized bouillon. Of this dilution, fowl a received 0..'> cubic centimetre 
subcutaueously over the pectoral muscle, and fowl h received 0.5 cubic centimetre 
into the pectoral muscle. 

Fowl h died May 4. At point of inoculation a yellowish membrauoua sequestrum 
beneath the skin over an area about 2 inches long ; beneath this the pectoral muscle 
was necrosed to a depth of about one-half inch. The surrouudiug muscle was 
sprinkled with punctiform hemorrhages. Heart muscle pale ; considerable serum in 
pericardial sac, which contains also several small straw-colored coagula. Liver 
fatty ; somewhat mottled, with grayish and bright red areas. Spleim enlarged ; friable. 
Kidneys i)ale ; fatty. The mucous membrane of intestines sonunvhat injected. 
CEsophagus and trachea normal. Lungs of a grayish color ; not consolidated. A very 
few oval bacteria, which did not exhibit the polar stain, were found in the spleen, 
liver and blood. Cultures from the blood and liver could not be distinginshed from 
cultures of swine-plague bacteria. 

Fowl a found dead May 11. Fowl much emaciated. At the point of iiioculation a 
Bcquestrum about 1 inch long lying beneath the skin ; subjacent muscle reddened. 
Heart muscle i)alc. Liver fatty ; quite firm. Spleen friable. Kidneys dark. The 
mucous membrane for a distance of about 4 inches below duodenum in the small in- 
testine has a roughened appearance, resembling superficial necrosis. A few oval 
germs found in liver and blood. An agar culture from the liver showed same charac- 
ters as cultures from fowl h. 

From the agar culture of the blood of fowl 1, agar and gelatine plate cultures were 
made. The agar plates developed colonies not distinguishable from swine-plague 
colonies. The gelatine i)lates remained free from growth. Other cultures have been 
made on the various media, but thus far no difi'ereuce has been detected between the 
growth of this germ and that of swine plague. 

Fowl No. 2. This fowl was not known to have been sick. Sternum showed evidtmce 
of an old injury. Liver fatty. Spleen enlarged. Kidneys normal. Mucous mem- 
brane of duodenum generally reddened, also sprinkled with minute bright red dots, 
probably injected villi. The mucous membrane of the mouth and cesophagns swollen, 
hyperaimic, and covered with a thin yellowish very friable exudate. The follicles 
and glands deeply reddened. The larynx and trachea contained a yellowish, croup- 
ous exudate in the form of a tube, easily removable in sections from one-fouith to I 
inch in length. The mucous membrane beneath tke exudate swollen ; cyanosed. It 
does not extend into the bronchi. Lungs normal. No bacti ria were found in the liver, 
spleen and blood. Cultures made from these organs remained clear. Agar plate cul- 
tures were made from the tracheal exudate. There developed a few chromogenic col- 
onies, and about five colonies of a very slender motile bacillus. 

Two rabbits inoculated subcutaueously with pieces of the exudate remained well. 

A rabbit inoculated in ear vein with 0.5 cubic centimetre of a bouillon culture of the 
bacillus obtained from the agarplates, and twomice inoculated subcutaueously w'ith 
the same culture, remained well. 



DESCRIPTION OF PLATES. 



ri.ATE I: 

Lungs of a healthy pig inflated, viewed from the left side ; a, principal lobe ; h, 
ventral lobe ; c, cephalic lobe; e, apex of heart. The dotted area bounded 
by the line xy indicates the portion usually involved in disease. 
Plvte II: 

The same luugs viewed from beneath (ventral, diaphragmatic surface); a, prin- 
ciiiallobe; 5, ventral lobe ; c, median or azygos lobe belonging to the right 
lung; e, apex of heart. The dotted area shows the average extent of the 
disease. 
Platk III: 

Lateral view of right lung of pig No. 407, outbreak IV. (See p. 24). The hep- 
atized regions are almost completely covered with a false membrane. 
Plate IV: 

The same lung as seen from the ventral surface. A portion of the diaphragm is 
fa.stened to it by means of exudate. The localization of the disease in the 
anterior (cephalic) and ventral jjortions is well brought out in these two 
plates. 

Plate V : 

Right lung from case 9, outbreak VII (see p. .38), showing hepatization of portion 

of cephalic, ventral, and afij.'uent principal lobe. Minute necrotic masses 

disseminated through the hepatized tissue. On the left more recent disease 

with marked interlobular cedema. 
Plate VI: 

Left lung of No. 2'v> (p. 46), showing extensive pneumonia after the injection of 

culture liquid into the right lung. There is in addition exudative pleuritis 

and pericarditis. 
Plate VII : 

Section of lung passing through bronchus. In the principal lobe around bron- 
chus the lung tissue is completely transformed into firm caseous masses. 

From outbreak IV. 
Plate VIII: 

Fig. 1. Section through one of the lobes of a diseased lung from outbreak IV, 

illustrative of the caseation so frequently encountered in this outbreak. 

The irregular patches of a homogeneous, faintly yellowish tint represent the 

cut surfaces of caseous masses. 
Fig. 2. A portion of the mucous membrane of the large intestine (outbreak IV), 

showing the peculiar isolated masses of exudate found in early cases of this 

outbreak. 

1614 11 161 



162 

Plate IX: 

Fig. 1. Collapse of groups of lobules in the principal lobe of a pig's lung. Fre- 
quently associated with bronchitis and lung worms. 

Fig. 2. Broncho-pneumonia. The cut surface of the lung tissue shows the 
occluded small air tubes as yellowish spots. The air vesicles or alveoli 
appear as minute yellowish dots in groups on the surface of the lungs, the 
color being due to the cell masses filling them up. The exudate plugging 
the air tubes is sometimes firm enough to be teased out in the form ot branch- 
ing cylinders. This form of lung disease is frequently associated with both 
hog cholera and swine plague, and may occur independently of them. 
Plate X: 

Heart exposed by removing pericardium. The surface of the heart (epicardium) 
is covered with exudation. The pericardium very much thickened by exud- 
ation of similar character. From case 12, outbreak VII. 
Plate XI : 

Fig. 1. Cover-glass preparation from spleen of rabbit inoculated with a particle 
of luug tissue from case 15, outbreak IX. Rabbit dead within 40 hours. 
Preparation stained in alkaline methylene blue and mounted in Xylol bal- 
sam. X 1,000. 

Fig. 2. Section from left lung of inoculated pig No. 275, outbreak VII (see p. 46), 
showing extensive cell infiltration of the alveoli and small air tubes. Tissue 
hardened in alcohol, stained in alkaline methylene blue. Mounted iu bal- 
sam. X 140. 

Fig. 3. A portion of the contents of an alveolus from the preceding figure highly 
magnified to show swine-plague bacteria. X 1,100. 

Fig. 4. From the liver of No. 454 inoculated subcutaneously with bacteria from 
outbreak IX (see p. 74). Intralobular capillary containing a mass of swine- 
plague bacteria. Section prepared and stained as indicated in the description 
of the preceding plate. X 1,100. 
Plate XII: 

Fig. 1. a, Surface colonies and deep colonies of swine-plague bacteria (outbreak 
IX) on an agar plate one week old. The small, round, and lenticular bodies 
represent the deep colonies, the larger ones the surface colonies; uatural 
size, b, A surface colony enlarged 17 diameters, showing reticulated center, 
and delicate radially striated periphery. 

Fig. 2. Two deep colonies from the same plate enlarged 17 diameters. 

Fig. 3. Colonies of swine-plague bacteria from outbreak I (1886), on a gelatine 
plate, 7 days old. X 60. 

Fig. 4. Agar tube culture of swine-plague bacteria (from outbreak VIII), about 
2 days old. Natural size. 



(;.iii,Mnix.iii'i 



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INDEX. 



Abdomen of swiue, injecticti of swine-plague bacteria into 29 45 

Agar-agar, growth of swine-plague bacteria on 88 

Age as predisposing to infection 133 

Air passages of domesticated animals, attenuated swine-plague bacteria in.. 109 

American investigations of swine plague, review of 118 

Animal parasites in swine plague 31.47, 104, 134 

Ascaris 134 

Attenuated swine-plague bacteria 94 

in sporadic cases of pneumonia and in 
septic diseases of swine, and in the upper 
air passages of healthy swine, and other 

domesticated animals 109 

Bacilli closely resembling hog-cholera bacilli found in swine-plague out- 
breaks 77 

Bacillus coli communis 11), 78 

Bacteria associated with swine plague 15, 77,80 

of swine plague. (See Swine Plague.) 

Bacteriological observations in swine plague 11, 'M~8i 

Barbone hufalino 143 

Billings, F. S., review of report on swine plague 118 

Biological characters of swine-plague bacteria 85 

Bleisch and Fiedeler, investigations of German swine plague by 129 

Boiling water as a disinfectant 14(; 

Bollinger, investigations of JVildsenche 141 

Bouillon cultures, advantages of 14 

growth of swine-plague bacteria in 88 

Breed as predisposing to infection • 133 

Buffalo disease in Italy resembling swine plague » 143 

Burrill, T. J., cultures of swine-plague bacteria sent by 124 

Carbolic acid as a disinfectant 145 

Caseation of the lungs in swine plagse 101 

Cats, bacteria in air passages of, resembling swine plague l.'')2 

Cattle and game atfected with disease resembling swiue plague 141 

bacteria in air passages of, resembling swine plague 15i 

Colonies of swine-plague bacteria ■. 87,88 

Comparison of bacteria obtained from air passages of domesticated animals. 156 

Conclusions 149 

Conditions Avhich favor and oppose swine plague 133 

Corrosive sublimate as a disinfectant 146 

Cultivation of swine-plague bacteria 87 

Cultures, bow made 12 

Digestive tract in swine plague 102 

Diphtheria and swine plague compared 117 

Distribution of swine-plague bacteria 135 

163 



164 

Page. 

Districtof Columbia, investigations in 23,31 

Disinfectants, application of 146 

for swine-plague bacteria 91 

Disinfection, rules for 145 

Dogs, bacteria in air passages of, resembling those of swine plague 153 

Drying destructive of swine-plague bacteria 90 

Echinorhynchus .» 134 

Feeding as predisposing to swine plague 134 

Fermentation tube, use of in the diagnosis of hog-cholera bacilli 81 

Food i n its relation to swine plague 137 

Fowl cholera 144 

disease caused by bacteria resembling those of swine plague 158 

Fowls inoculated with swine plague bacteria 21, 77, 96 

Galtier, investigation of swine disease in France by 143 

Gelatine, growth of swine-plague bacteria on 87 

German investigations of swine plague 125 

German swine plague 31,85, 122, 125 

inoculation of rabbits and pigs with 123 

Guinea-pigs, inoculated with swine-plague bacteria 21,47,76,95 

pneumonia and pleuritisin, caused by bacteria resembling those 

of swine plague 158 

Hog-cholera bacilli 34,35,39,40,41,77 

attenuated varieties of 77, 138 

Hog cholera, its relation to swine plague 138 

post-mortem notes in 56 

Hog cholera and swiue plague (See Swine Plague and Hog Cholera.) 

bacteria inoculated together 106 

on same farm but not intermingled 47 

and typhoid fever compared 108 

Hlinois, investigations in 20 

immunity produced in rabbits with sterilized cultures 148 

Indol and pbenol in swine-plague cultures 89 

Inoculation of smaller animals 13 

small animals with swine-plague bacteria 93 

swine with cultures of swine-plague bacteria 21,29,45,71,97 

German swine plague 128 

Intestinal lesions in swine plague 98,102,103 

Intestines of swine 17 

Intra-abdominal injection of swine-plague bacteria 29, 45 

Intra-thoracic inoculation of swine-plague bacteria 21,45, 71, 74, 113, 121 

lutra- venous inoculation of swine-plague bacteria 71,75, 128 

In troductory 9 

Iowa, investigations in 23,28 

Jeffries, J. A., investigations of swine plague by 123 

Joint disease produced by intra- venous injection of swine-plague bacteria. .. 75 

Kitt, investigations of cattle disease resembling swine plague by 142 

Lime as a disinfectant 91, 145 

Loffler, investigations of swine plague by 125 

Lung disease in swine plague 98 

Lungs of swine, description of 17 

injection of swine-plague bacteria into 21,29,45, 71, 113 

Lung worms associated with swine plague 104, 134 

in outbreaks VII and VIII 31,47 

Malignant oedema bacilli found in swine-plague outbreak 80 

Maryland, investigations in 27 



165 

Pajie. 

Mercuric cliloride as a disinfectant 14G 

Mice inoculated with swine-plague bacteria 21, 47,77 

Milk, growth of swine-plague bacteria in y9 

Moore, Dr. V. A., report on the presence of septic bacteria jnobably identi- 
cal with those of swine plague, in the upper air passages of domesticated 

animals other than swine 151 

Morphological characters of swine-plague bacteria 85 

Necrosis of the lungs in swine plague 101 

New Jersey, investigations in 57 

Parasites in their relation to swine plague l;?4 

Pathogenic action of swine-plague bacteria 93 

Peritonitis in swine 112 

Peters, F., investigations of German swine plague 131 

Phenol and indol in swine-plague cultures 89 

Pigeons inoculated with swine-plague bacteria 21, 77, 96 

Plate cultures, limitations of 14 

Plales, description of 161 

Pneumonia in cattle resembling swine plague 144 

guinea-pigs following inoculation with swine-plague bacteria. 47 

man and swine plague compared 117 

rabbits following inoculation with swine-pl.igue bacteria 94, 124 

swine plague 98 

sporadic cases of 109, 111, 151 

Post-mortem notes in swine plague 24,32, 49,58,69,72,73, 74,75,76 

I'ractical observations on the prevention of swine plague 133 

Preventive inoculation for swine plague 148 

Rabbits inoculated with hog-cholera bacilli 35, 4ii,56, 79 

swine-plague bacteria .... 1(3, 19, 21, 25, 32, 38. 39, 49, 54, 55, 56, 
60, 65, rt3, 93, 111-116, 124, 127, 128 

Rabbit septicaemia 125, 144 

Saliva of domesticated animals containing disease germs 109, 151 

Schiveineseuche. (See German swine plague.) 

Schiitz, investigations of swine plague by 126 

Soil, destruction of swine-plague bacteria in 91 

Staining of swine-plague bacteria f^5 

Strongylus paradoxus (lung worms) 134 

Subcutaneous inoculation of swine-plague bacteria 21,45, 71.74, 113, 128 

Sulphuric acid as a disinfectant 146 

Swine, injection into lungs of, with swine-plague bacteria 21, 29, 45. 71, 113 

veins of, with swine- plague bacteria 71,75, 128 

Swine inoculated with hog-cholera bacilli 80, 97 

swine-plague bacteria 21,29,45,71,97,106,113 

large intestine of 17 

lungs of 17 

subcutaneous inoculation with swine-plague bacteria 21,45,71,74,113,128 

Swine plague and hog cholera compared 105 

intermingled, how distinguished 14 

and pneumonia in man compared 108 

as related to diseases of other domesticated animals 141 

associated with hog cholera 14, 20, 23, 27, 31, 77, 82, 84, 103, 104 

bacteria, attenuated varieties of 15, .55,94, 1:58 

carried by young and old animals 110, 114 

cultivation of -. 87 

distribution and transmission of 135 



166 

Page. 

Swine plague bacteria, general characters of 85 

injection into abdomen of pigs 29,45 

lung-! of pigs 21,29,45,71,113 

veins of pigs 71, 75, 128 

under skin of pigs 21, 45, 71, 74, 113, 128 

inoculated into small animals 93 

non-motile ." 86 

objects which may carry 145 

pathogenic action of 96 

producing phenol and indol in cultures 89 

readily destroyed by various agents 90 

caused by direct infection 69 

conditions which may favor and oppose 133 

in Germany 125 

iavestigations by Billings, F. S 118 

Bleisch and Fiedeler 129 

Burrill, T.J 124 

Jeffries 123 

Loffler 125 

Peters 131 

Schiitz 126 

Welch and Clement 122 

in District of Cohinibia 2 5,31 

Germany 125 

Illinois 20,124 

Iowa , 23,28 

Maryland 27,122 

Massach usetts 123 

Missouri 82 

New Jersey 57 

its relation to hog cholera 106, 138 

modified by vaccination 94 

outbreaks of 19,20,23,27,28,31,47.57,82,84 

preveutiou of 133, 145 

preventive inoculation for 148 

treatment ofig 146 

with reference to human disease 108 

Table showing difference between hog-cholera and swine-plague bacteria . .. 92, 105 

distribution of hog cholera and swine plague 140 

Temperature at which swine-plague bacteria multiply 89 

Treatment of swine plague 146 

Varieties of hog-cbolera bacilli 138 

swine-plague bacteria 93, 136 

Virulence of bacteria, importance of 117 

swine-plague bacteria 135, 144 

Water, destruction of swine-plague bacteria in 92 

Welch, W. H., and Clement, A, W., report on swine plague 122 

Whitewash as a disinfectant 146 

Wildseuche 141 



